feat: support hosting .well-known from Conduit

Co-authored-by: Matthias Ahouansou <matthias@ahouansou.cz>

src/api/client_server/well_known.rs

@@ -0,0 +1,22 @@
+use ruma::api::client::discovery::discover_homeserver::{
+    self, HomeserverInfo, SlidingSyncProxyInfo,
+};
+
+use crate::{services, Result, Ruma};
+
+/// # `GET /.well-known/matrix/client`
+///
+/// Returns the client server discovery information.
+pub async fn well_known_client(
+    _body: Ruma<discover_homeserver::Request>,
+) -> Result<discover_homeserver::Response> {
+    let client_url = services().globals.well_known_client();
+
+    Ok(discover_homeserver::Response {
+        homeserver: HomeserverInfo {
+            base_url: client_url.clone(),
+        },
+        identity_server: None,
+        sliding_sync_proxy: Some(SlidingSyncProxyInfo { url: client_url }),
+    })
+}