object CommentTable : LongIdTable() {
        val comment = text("comment")
        val entityType = varchar("entityType", 128)
        val entityID = long("entityId")
    }
    
    class Comment(id: EntityID<Long>) : LongEntity(id) {
        var comment by CommentTable.comment
        private var entityType by CommentTable.entityType
        private var entityId by CommentTable.entityID
        
        companion object : LongEntityClass<Comment>(CommentTable) {
            fun addComment(entity: CommentsAware, comment: String) = Comment.new { 
                this.comment = comment
                this.entityId = entity.entityId
                this.entityType = entity.entityType
            }
        }
    }
    
    interface CommentsAware {
        val entityId : Long
        val entityType: String
        
        fun getComments() = Comment.find { CommentTable.entityType eq entityType and (CommentTable.entityID eq entityId) } 
    }
    
    class User(id: EntityID<Long>) : LongEntity(id), CommentsAware {
        override val entityId: Long get() = id.value
        override val entityType: String = "user"
    }