Make room type into an enum

lib/models/content/create.dart

@@ -19,13 +19,19 @@ abstract class CreateContent extends Content with _$CreateContent {
     @JsonKey(name: "m.federate") @Default(true) bool federated,
 
     @Default("1") String roomVersion,
-    String? type,
+    @JsonKey(unknownEnumValue: RoomType.room) RoomType? type,
   }) = _CreateContent;
 
   factory CreateContent.fromJson(Map<String, Object?> json) =>
       _$CreateContentFromJson(json);
 }
 
+enum RoomType {
+  room,
+  @JsonValue("m.space")
+  space,
+}
+
 @freezed
 abstract class PreviousRoom with _$PreviousRoom {
   const factory PreviousRoom({required String roomId}) = _PreviousRoom;