Remove unused response bodies from a number of API endpoints.

This removes the response body from the following methods:

* `POST /api/setup`
* `POST /api/auth/login`
* `POST /api/invite/:id`
* `POST /api/password`

The bodies returned from these methods were something of a rough guess as to what might be useful. Actual client development has shown that we don't use _any_ of the data from any of these API responses, so let's not tie ourselves to future compatibility by continuing to send them. We can add a body to a bodyless method a _lot_ more easily than we can change the body of a method that already returns one, after all.

These changes are not backwards compatible for clients which care about the existing bodies. To my knowledge, there are no such clients; the included client definitely doesn't care.

## Internals

Not only does this change stop returning bodies at the API surface, but it also stops retrieving and returning values used internally to construct those responses, simplifying the code a bit in the process.

One side effect of this is that tests that need to log in a user now need to manually verify the returned token secret, to convert it back into a user, whereas the previous versions returned both a token secret and a user during password login. I don't love the increase in the size of the tests, but I think it's the right tradeoff (and this change is code net-negative anyways).

Merges no-content into main.

2 files changed, 7 insertions, 8 deletions

diff --git a/src/user/handlers/login/mod.rs b/src/user/handlers/login/mod.rs
index da88885..d3e0e8c 100644
--- a/src/user/handlers/login/mod.rs
+++ b/src/user/handlers/login/mod.rs
@@ -7,11 +7,11 @@ use axum::{
 use crate::{
     app::App,
     clock::RequestedAt,
+    empty::Empty,
     error::Internal,
     name::Name,
     password::Password,
     token::{app, extract::IdentityCookie},
-    user::User,
 };
 
 #[cfg(test)]
@@ -22,14 +22,14 @@ pub async fn handler(
     RequestedAt(now): RequestedAt,
     identity: IdentityCookie,
     Json(request): Json<Request>,
-) -> Result<(IdentityCookie, Json<User>), Error> {
-    let (user, secret) = app
+) -> Result<(IdentityCookie, Empty), Error> {
+    let secret = app
         .tokens()
         .login(&request.name, &request.password, &now)
         .await
         .map_err(Error)?;
     let identity = identity.set(secret);
-    Ok((identity, Json(user)))
+    Ok((identity, Empty))
 }
 
 #[derive(serde::Deserialize)]
diff --git a/src/user/handlers/login/test.rs b/src/user/handlers/login/test.rs
index b8f24f6..bdd1957 100644
--- a/src/user/handlers/login/test.rs
+++ b/src/user/handlers/login/test.rs
@@ -1,6 +1,6 @@
 use axum::extract::{Json, State};
 
-use crate::{test::fixtures, token::app};
+use crate::{empty::Empty, test::fixtures, token::app};
 
 #[tokio::test]
 async fn correct_credentials() {
@@ -17,14 +17,13 @@ async fn correct_credentials() {
         name: name.clone(),
         password,
     };
-    let (identity, Json(response)) =
+    let (identity, Empty) =
         super::handler(State(app.clone()), logged_in_at, identity, Json(request))
             .await
             .expect("logged in with valid credentials");
 
     // Verify the return value's basic structure
 
-    assert_eq!(name, response.name);
     let secret = identity
         .secret()
         .expect("logged in with valid credentials issues an identity cookie");
@@ -38,7 +37,7 @@ async fn correct_credentials() {
         .await
         .expect("identity secret is valid");
 
-    assert_eq!(response, validated_login);
+    assert_eq!(name, validated_login.name);
 }
 
 #[tokio::test]