Convert the `Conversations` component into a freestanding struct.

Unlike the previous example, this involves cloning an event broadcaster, as well. This is, per the documentation, how the type may be used. From <https://docs.rs/tokio/latest/tokio/sync/broadcast/fn.channel.html>:

> The Sender can be cloned to send to the same channel from multiple points in the process or it can be used concurrently from an `Arc`.

The language is less firm than the language sqlx uses for its pool, but the intent is clear enough, and it works in practice.

4 files changed, 55 insertions, 40 deletions

diff --git a/src/conversation/handlers/create/mod.rs b/src/conversation/handlers/create/mod.rs
index 18eca1f..2b7fa39 100644
--- a/src/conversation/handlers/create/mod.rs
+++ b/src/conversation/handlers/create/mod.rs
@@ -5,9 +5,8 @@ use axum::{
 };
 
 use crate::{
-    app::App,
     clock::RequestedAt,
-    conversation::{Conversation, app},
+    conversation::{Conversation, app, app::Conversations},
     error::Internal,
     name::Name,
     token::extract::Identity,
@@ -17,13 +16,12 @@ use crate::{
 mod test;
 
 pub async fn handler(
-    State(app): State<App>,
+    State(conversations): State<Conversations>,
     _: Identity, // requires auth, but doesn't actually care who you are
     RequestedAt(created_at): RequestedAt,
     Json(request): Json<Request>,
 ) -> Result<Response, Error> {
-    let conversation = app
-        .conversations()
+    let conversation = conversations
         .create(&request.name, &created_at)
         .await
         .map_err(Error)?;
diff --git a/src/conversation/handlers/create/test.rs b/src/conversation/handlers/create/test.rs
index bc05b00..380bb13 100644
--- a/src/conversation/handlers/create/test.rs
+++ b/src/conversation/handlers/create/test.rs
@@ -22,10 +22,14 @@ async fn new_conversation() {
 
     let name = fixtures::conversation::propose();
     let request = super::Request { name: name.clone() };
-    let super::Response(response) =
-        super::handler(State(app.clone()), creator, fixtures::now(), Json(request))
-            .await
-            .expect("creating a conversation in an empty app succeeds");
+    let super::Response(response) = super::handler(
+        State(app.conversations()),
+        creator,
+        fixtures::now(),
+        Json(request),
+    )
+    .await
+    .expect("creating a conversation in an empty app succeeds");
 
     // Verify the structure of the response
 
@@ -77,10 +81,14 @@ async fn duplicate_name() {
     let request = super::Request {
         name: conversation.name.clone(),
     };
-    let super::Error(error) =
-        super::handler(State(app.clone()), creator, fixtures::now(), Json(request))
-            .await
-            .expect_err("duplicate conversation name should fail the request");
+    let super::Error(error) = super::handler(
+        State(app.conversations()),
+        creator,
+        fixtures::now(),
+        Json(request),
+    )
+    .await
+    .expect_err("duplicate conversation name should fail the request");
 
     // Verify the structure of the response
 
@@ -110,10 +118,14 @@ async fn conflicting_canonical_name() {
     let request = super::Request {
         name: conflicting_name.clone(),
     };
-    let super::Error(error) =
-        super::handler(State(app.clone()), creator, fixtures::now(), Json(request))
-            .await
-            .expect_err("duplicate conversation name should fail the request");
+    let super::Error(error) = super::handler(
+        State(app.conversations()),
+        creator,
+        fixtures::now(),
+        Json(request),
+    )
+    .await
+    .expect_err("duplicate conversation name should fail the request");
 
     // Verify the structure of the response
 
@@ -135,7 +147,7 @@ async fn invalid_name() {
     let name = fixtures::conversation::propose_invalid_name();
     let request = super::Request { name: name.clone() };
     let super::Error(error) = crate::conversation::handlers::create::handler(
-        State(app.clone()),
+        State(app.conversations()),
         creator,
         fixtures::now(),
         Json(request),
@@ -163,7 +175,7 @@ async fn name_reusable_after_delete() {
 
     let request = super::Request { name: name.clone() };
     let super::Response(response) = super::handler(
-        State(app.clone()),
+        State(app.conversations()),
         creator.clone(),
         fixtures::now(),
         Json(request),
@@ -181,10 +193,14 @@ async fn name_reusable_after_delete() {
     // Call the endpoint (second time)
 
     let request = super::Request { name: name.clone() };
-    let super::Response(response) =
-        super::handler(State(app.clone()), creator, fixtures::now(), Json(request))
-            .await
-            .expect("creation succeeds after original conversation deleted");
+    let super::Response(response) = super::handler(
+        State(app.conversations()),
+        creator,
+        fixtures::now(),
+        Json(request),
+    )
+    .await
+    .expect("creation succeeds after original conversation deleted");
 
     // Verify the structure of the response
 
@@ -212,7 +228,7 @@ async fn name_reusable_after_expiry() {
 
     let request = super::Request { name: name.clone() };
     let super::Response(_) = super::handler(
-        State(app.clone()),
+        State(app.conversations()),
         creator.clone(),
         fixtures::ancient(),
         Json(request),
@@ -230,10 +246,14 @@ async fn name_reusable_after_expiry() {
     // Call the endpoint (second time)
 
     let request = super::Request { name: name.clone() };
-    let super::Response(response) =
-        super::handler(State(app.clone()), creator, fixtures::now(), Json(request))
-            .await
-            .expect("creation succeeds after original conversation expired");
+    let super::Response(response) = super::handler(
+        State(app.conversations()),
+        creator,
+        fixtures::now(),
+        Json(request),
+    )
+    .await
+    .expect("creation succeeds after original conversation expired");
 
     // Verify the structure of the response
 
diff --git a/src/conversation/handlers/delete/mod.rs b/src/conversation/handlers/delete/mod.rs
index 272165a..231e433 100644
--- a/src/conversation/handlers/delete/mod.rs
+++ b/src/conversation/handlers/delete/mod.rs
@@ -5,9 +5,8 @@ use axum::{
 };
 
 use crate::{
-    app::App,
     clock::RequestedAt,
-    conversation::{self, app, handlers::PathInfo},
+    conversation::{self, app, app::Conversations, handlers::PathInfo},
     error::{Internal, NotFound},
     token::extract::Identity,
 };
@@ -16,14 +15,12 @@ use crate::{
 mod test;
 
 pub async fn handler(
-    State(app): State<App>,
+    State(conversations): State<Conversations>,
     Path(conversation): Path<PathInfo>,
     RequestedAt(deleted_at): RequestedAt,
     _: Identity,
 ) -> Result<Response, Error> {
-    app.conversations()
-        .delete(&conversation, &deleted_at)
-        .await?;
+    conversations.delete(&conversation, &deleted_at).await?;
 
     Ok(Response { id: conversation })
 }
diff --git a/src/conversation/handlers/delete/test.rs b/src/conversation/handlers/delete/test.rs
index 2718d3b..e9e882a 100644
--- a/src/conversation/handlers/delete/test.rs
+++ b/src/conversation/handlers/delete/test.rs
@@ -14,7 +14,7 @@ pub async fn valid_conversation() {
 
     let deleter = fixtures::identity::create(&app, &fixtures::now()).await;
     let response = super::handler(
-        State(app.clone()),
+        State(app.conversations()),
         Path(conversation.id.clone()),
         fixtures::now(),
         deleter,
@@ -52,7 +52,7 @@ pub async fn invalid_conversation_id() {
     let deleter = fixtures::identity::create(&app, &fixtures::now()).await;
     let conversation = fixtures::conversation::fictitious();
     let super::Error(error) = super::handler(
-        State(app.clone()),
+        State(app.conversations()),
         Path(conversation.clone()),
         fixtures::now(),
         deleter,
@@ -81,7 +81,7 @@ pub async fn conversation_deleted() {
 
     let deleter = fixtures::identity::create(&app, &fixtures::now()).await;
     let super::Error(error) = super::handler(
-        State(app.clone()),
+        State(app.conversations()),
         Path(conversation.id.clone()),
         fixtures::now(),
         deleter,
@@ -110,7 +110,7 @@ pub async fn conversation_expired() {
 
     let deleter = fixtures::identity::create(&app, &fixtures::now()).await;
     let super::Error(error) = super::handler(
-        State(app.clone()),
+        State(app.conversations()),
         Path(conversation.id.clone()),
         fixtures::now(),
         deleter,
@@ -144,7 +144,7 @@ pub async fn conversation_purged() {
 
     let deleter = fixtures::identity::create(&app, &fixtures::now()).await;
     let super::Error(error) = super::handler(
-        State(app.clone()),
+        State(app.conversations()),
         Path(conversation.id.clone()),
         fixtures::now(),
         deleter,
@@ -170,7 +170,7 @@ pub async fn conversation_not_empty() {
 
     let deleter = fixtures::identity::create(&app, &fixtures::now()).await;
     let super::Error(error) = super::handler(
-        State(app.clone()),
+        State(app.conversations()),
         Path(conversation.id.clone()),
         fixtures::now(),
         deleter,