Editing topic tags as a list in a Phoenix form

This fkey constraint is on the join table, not on the topics!

Trying to delete topics from the topics index page produces an error:

** (Ecto.ConstraintError) constraint error when attempting to delete struct:

* entities_topics_topic_id_fkey (foreign_key_constraint)

If you would like to stop this constraint violation from raising an
exception and instead add it as an error to your changeset, please
call foreign_key_constraint/3 on your changeset with the constraint
:name as an option.

The changeset has not defined any constraint.

I cannot find the correct way to display an appropriate message for the error. Adding something like |> foreign_key_constraint(:entities, name: :entities_topics_topic_id_fkey, message: "There still is content related to that Topic") to the Topic changeset doesn't seem to work. Is this something discussed in the followup video's?

Thank you, this worked:

def delete_changeset(topic) do    
   topic    
     |> change()    
     |> foreign_key_constraint(:topic_id,      
       name: :entities_topics_topic_id_fkey,      
       message: "There still is content related to that Topic"    
      ) 
end

No problem!