refactor max channels per team enforcement (#7690)

store/store.go

@@ -104,7 +104,7 @@ type TeamStore interface {
 }
 
 type ChannelStore interface {
-	Save(channel *model.Channel) StoreChannel
+	Save(channel *model.Channel, maxChannelsPerTeam int64) StoreChannel
 	CreateDirectChannel(userId string, otherUserId string) StoreChannel
 	SaveDirectChannel(channel *model.Channel, member1 *model.ChannelMember, member2 *model.ChannelMember) StoreChannel
 	Update(channel *model.Channel) StoreChannel