feat: Support creating custom v12 room IDs

src/api/client/room/create.rs

@@ -238,6 +238,7 @@ pub(crate) async fn create_room_route(
 				event_type: TimelineEventType::RoomCreate,
 				content: to_raw_value(&create_content)?,
 				state_key: Some(StateKey::new()),
+				timestamp: body.origin_server_ts,
 				..Default::default()
 			},
 			sender_user,
@@ -256,6 +257,14 @@ pub(crate) async fn create_room_route(
 		},
 	};
 	drop(state_lock);
+	if let Some(expected_room_id) = body.room_id.as_ref() {
+		if expected_room_id.as_str() != room_id.as_str() {
+			return Err!(Request(InvalidParam(
+				"Custom room ID {expected_room_id} does not match the generated room ID \
+				 {room_id}.",
+			)));
+		}
+	}
 	debug!("Room created with ID {room_id}");
 	let state_lock = services.rooms.state.mutex.lock(&room_id).await;
 

src/service/rooms/timeline/create.rs

@@ -15,7 +15,6 @@ use futures::{StreamExt, TryStreamExt, future, future::ready};
 use ruma::{
 	CanonicalJsonObject, CanonicalJsonValue, OwnedEventId, OwnedRoomId, RoomId, RoomVersionId,
 	UserId,
-	canonical_json::to_canonical_value,
 	events::{StateEventType, TimelineEventType, room::create::RoomCreateEventContent},
 	uint,
 };
@@ -210,7 +209,7 @@ pub async fn create_hash_and_sign_event(
 		} else {
 			Some(to_raw_value(&unsigned)?)
 		},
-		hashes: EventHash { sha256: "aaa".to_owned() },
+		hashes: EventHash { sha256: String::new() },
 		signatures: None,
 	};
 
@@ -269,12 +268,6 @@ pub async fn create_hash_and_sign_event(
 		},
 	}
 
-	pdu_json.insert(
-		"origin".to_owned(),
-		to_canonical_value(self.services.globals.server_name())
-			.expect("server name is a valid CanonicalJsonValue"),
-	);
-
 	trace!("hashing and signing event {}", pdu.event_id);
 	if let Err(e) = self
 		.services