Adds support for GMs in shared channels (#31403)

* Adds support for GMs in shared channels

* Fix linter

* Remove creatorID from slack call

---------

Co-authored-by: Miguel de la Cruz <miguel@ctrlz.es>

server/channels/store/sqlstore/channel_store.go

@@ -616,7 +616,11 @@ func (s SqlChannelStore) upsertPublicChannelT(transaction *sqlxTxWrapper, channe
 }
 
 // Save writes the (non-direct) channel to the database.
-func (s SqlChannelStore) Save(rctx request.CTX, channel *model.Channel, maxChannelsPerTeam int64) (_ *model.Channel, err error) {
+func (s SqlChannelStore) Save(rctx request.CTX, channel *model.Channel, maxChannelsPerTeam int64, channelOptions ...model.ChannelOption) (_ *model.Channel, err error) {
+	for _, option := range channelOptions {
+		option(channel)
+	}
+
 	if channel.DeleteAt != 0 {
 		return nil, store.NewErrInvalidInput("Channel", "DeleteAt", channel.DeleteAt)
 	}