client-api: Add support for mutual rooms endpoint (MSC2666)

crates/ruma-client-api/Cargo.toml

@@ -19,6 +19,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 compat = []
 unstable-exhaustive-types = []
 unstable-msc2246 = []
+unstable-msc2666 = []
 unstable-msc2448 = []
 unstable-msc2654 = []
 unstable-msc2675 = []

crates/ruma-client-api/src/membership.rs

@@ -10,6 +10,8 @@ pub mod joined_members;
 pub mod joined_rooms;
 pub mod kick_user;
 pub mod leave_room;
+#[cfg(feature = "unstable-msc2666")]
+pub mod mutual_rooms;
 pub mod unban_user;
 
 use std::collections::BTreeMap;

crates/ruma-client-api/src/membership/mutual_rooms.rs

@@ -0,0 +1,47 @@
+//! `GET /_matrix/client/*/user/mutual_rooms/{user_id}`
+
+pub mod unstable {
+    //! `/unstable/` ([spec])
+    //!
+    //! [spec]: https://github.com/matrix-org/matrix-spec-proposals/blob/hs/shared-rooms/proposals/2666-get-rooms-in-common.md
+
+    use ruma_common::{api::ruma_api, OwnedRoomId, UserId};
+
+    ruma_api! {
+        metadata: {
+            description: "Get mutual rooms with another user.",
+            method: GET,
+            name: "mutual_rooms",
+            unstable_path: "/_matrix/client/unstable/uk.half-shot.msc2666/user/mutual_rooms/:user_id",
+            rate_limited: true,
+            authentication: AccessToken,
+        }
+
+        request: {
+            /// The user to search mutual rooms for.
+            #[ruma_api(path)]
+            pub user_id: &'a UserId,
+        }
+
+        response: {
+            /// A list of rooms the user is in together with the authenticated user.
+            pub joined: Vec<OwnedRoomId>,
+        }
+
+        error: crate::Error
+    }
+
+    impl<'a> Request<'a> {
+        /// Creates a new `Request` with the given user id.
+        pub fn new(user_id: &'a UserId) -> Self {
+            Self { user_id }
+        }
+    }
+
+    impl Response {
+        /// Creates a `Response` with the given room ids.
+        pub fn new(joined: Vec<OwnedRoomId>) -> Self {
+            Self { joined }
+        }
+    }
+}

crates/ruma/Cargo.toml

@@ -124,6 +124,7 @@ unstable-msc2448 = [
     "ruma-federation-api?/unstable-msc2448"
 ]
 unstable-msc2654 = ["ruma-client-api?/unstable-msc2654"]
+unstable-msc2666 = ["ruma-client-api?/unstable-msc2666"]
 unstable-msc2675 = [
     "ruma-client-api?/unstable-msc2675",
     "ruma-common/unstable-msc2675",
@@ -164,6 +165,7 @@ __ci = [
     "unstable-pre-spec",
     "unstable-msc1767",
     "unstable-msc2448",
+    "unstable-msc2666",
     "unstable-msc2654",
     "unstable-msc2675",
     "unstable-msc2676",