message: add suffixes from provider to room and completions
  this prevents the not working when not typing an extra space
diff: @@ -102,9 +102,9 @@ export default class AutocompleteWrapperModel {
  const text = completion.completion;
  switch (completion.type) {
  case "room":
  - return [this._partCreator.roomPill(completionId)];
  + return [this._partCreator.roomPill(completionId), this._partCreator.plain(completion.suffix)];
  case "at-room":
  - return [this._partCreator.atRoomPill(completionId)];
  + return [this._partCreator.atRoomPill(completionId), this._partCreator.plain(completion.suffix)];
  case "user":
  // not using suffix here, because we also need to calculate
  // the suffix when clicking a display name to insert a mention,
  