Unify `setup_required` middlewares.

The two middlewares were identical but for the specific `IntoResponse` impl used to generate the response when setup has not been completed. However, unifying them while still using `from_fn_with_state` lead to this horrorshow:

    .route_layer(middleware::from_fn_with_state(
        app.clone(),
        |state, req, next| {
            setup::middeware::setup_required(UNAVAILABLE, state, req, next)
        }
    ))

It's a lot to read, and it surfaces the entire signature of a state-driven middleware `fn` into the call site solely to close over one argument (`UNAVAILABLE`).

Rather than doing that, I've converted this middleware into a full blown Tower middleware, following <https://docs.rs/axum/latest/axum/middleware/index.html#towerservice-and-pinboxdyn-future>. I considered taking this further and implementing a custom future to remove the allocation for `Box::pin`, but honestly, that allocation isn't hurting anyone and this code already got long enough in the translation.

The new API looks like:

    .route_layer(setup::Required::or_unavailable(app.clone()))

Or like:

    .route_layer(setup::Required::with_fallback(app.clone(), RESPONSE))

One thing I would have liked to have avoided is the additional `app.clone()` argument, but there isn't a way to extract the _state_ from a request inside of an Axum middleware. It has to be passed in externally - that's what `from_fn_with_state` is doing under the hood, as well. Using `State` as an extractor doesn't work; the `State` extractor is special in a _bunch_ of ways, and this is one of them. Other extractors would work. Realistically, I'd probably want to explore interfaces like

    .route_layer(setup::Required(app).or_unavailable())

 or

    .route_layer(app.setup().required().or_unavailable())

3 files changed, 6 insertions, 19 deletions

diff --git a/src/ui/middleware.rs b/src/ui/middleware.rs
deleted file mode 100644
index f60ee1c..0000000
--- a/src/ui/middleware.rs
+++ /dev/null
@@ -1,15 +0,0 @@
-use axum::{
-    extract::{Request, State},
-    middleware::Next,
-    response::{IntoResponse, Redirect, Response},
-};
-
-use crate::{app::App, error::Internal};
-
-pub async fn setup_required(State(app): State<App>, request: Request, next: Next) -> Response {
-    match app.setup().completed().await {
-        Ok(true) => next.run(request).await,
-        Ok(false) => Redirect::to("/setup").into_response(),
-        Err(error) => Internal::from(error).into_response(),
-    }
-}
diff --git a/src/ui/mod.rs b/src/ui/mod.rs
index f8caa48..e834bba 100644
--- a/src/ui/mod.rs
+++ b/src/ui/mod.rs
@@ -1,6 +1,5 @@
 mod assets;
 mod error;
-mod middleware;
 mod mime;
 mod routes;
 
diff --git a/src/ui/routes/mod.rs b/src/ui/routes/mod.rs
index 80dc1e5..328eb73 100644
--- a/src/ui/routes/mod.rs
+++ b/src/ui/routes/mod.rs
@@ -1,6 +1,6 @@
-use axum::{Router, middleware, routing::get};
+use axum::{Router, response::Redirect, routing::get};
 
-use crate::{app::App, ui::middleware::setup_required};
+use crate::app::App;
 
 mod ch;
 mod get;
@@ -21,7 +21,10 @@ pub fn router(app: &App) -> Router<App> {
             .route("/login", get(login::get::handler))
             .route("/ch/{channel}", get(ch::channel::get::handler))
             .route("/invite/{invite}", get(invite::invite::get::handler))
-            .route_layer(middleware::from_fn_with_state(app.clone(), setup_required)),
+            .route_layer(crate::setup::Required::with_fallback(
+                app.clone(),
+                Redirect::to("/setup"),
+            )),
     ]
     .into_iter()
     .fold(Router::default(), Router::merge)