tests: cap actix workers to prevent fd exhaustion

cargo test was failing with too many open files because each test server
spawned a worker per CPU, quickly exhausting file descriptors when tests ran
in parallel. Set test servers to one worker so they use a bounded number of
sockets/threads, avoiding fd exhaustion and letting OIDC and migration tests
start reliably.

Author: lovasoa

tests/common/mod.rs

@@ -158,6 +158,7 @@ pub fn start_echo_server(shutdown: oneshot::Receiver<()>) -> (JoinHandle<()>, u1
             Ok(req.into_response(resp))
         }))
     })
+    .workers(1)
     .listen(listener)
     .unwrap()
     .shutdown_timeout(1)

tests/oidc/mod.rs

@@ -201,6 +201,7 @@ impl FakeOidcProvider {
                 .route("/jwks", web::get().to(jwks_endpoint))
                 .route("/token", web::post().to(token_endpoint))
         })
+        .workers(1)
         .listen(listener)
         .unwrap()
         .shutdown_timeout(1)