I have a Content object which refers to a set of Tag objects in a ManyToMany relationship. As part of persisting a new Content object I look in PostgreSQL to see if the Tag alr
change the configuration of your relation in content entity to this:
@JoinTable(name = "content_tag", joinColumns = @JoinColumn(name = "content_id"), inverseJoinColumns = @JoinColumn(name="tag_id") )