MBS-12780: Fix allowNew check for AddRelationship (#2770)

This was checking for the entity0 and entity1 passed outside
the relationship itself - which we were also adding
to the relationship data for display.
But we were only passing this if the ID was not defined
in the first place, so this check was nonsensical AFAICT.
In fact, I cannot find any reason to pass entity0 and entity1
outside the relationship, since we're already passing them inside it.

I'm also removing the source_type and target_type that
I had added in 9b0eae3
since AFAICT we're again not using those, but the ones
inside the relationship object.

lib/MusicBrainz/Server/Edit/Relationship/Create.pm

@@ -181,14 +181,14 @@ sub build_display_data
     my $loaded_entity_0 = $loaded->{$model0}{$entity0_gid_or_id} if $entity0_gid_or_id;
     my $entity0 = $loaded_entity_0 ||
         $self->c->model($model0)->_entity_class->new(
-            id => 0,
+            id => $self->data->{entity0}{id} // 0,
             name => $self->data->{entity0}{name}
         );
     my $entity1_gid_or_id = gid_or_id($self->data->{entity1});
     my $loaded_entity_1 = $loaded->{$model1}{$entity1_gid_or_id} if $entity1_gid_or_id;
     my $entity1 = $loaded_entity_1 ||
         $self->c->model($model1)->_entity_class->new(
-            id => 0,
+            id => $self->data->{entity1}{id} // 0,
             name => $self->data->{entity1}{name}
         );
     my $entity0_credit = $self->data->{entity0_credit} // '';
@@ -238,10 +238,6 @@ sub build_display_data
             grep { !exists $loaded->{LinkAttributeType}{$_->{type}{id}} }
                 @{ $self->data->{attributes} // [] }
         )),
-        source_type => $type0,
-        target_type => $type1,
-        entity0 => defined $entity0->id ? undef : to_json_object($entity0),
-        entity1 => defined $entity1->id ? undef : to_json_object($entity1),
     }
 }
 

root/edit/details/AddRelationship.js

@@ -17,19 +17,15 @@ type Props = {
 };
 
 const AddRelationship = ({edit}: Props): React.MixedElement => {
-  const relationship = {
-    ...edit.display_data.relationship,
-    entity0: edit.display_data.entity0,
-    entity1: edit.display_data.entity1,
-  };
+  const relationship = edit.display_data.relationship;
   return (
     <table className="details add-relationship">
       <tr>
         <th>{l('Relationship:')}</th>
         <td>
           <Relationship
-            allowNewEntity0={!edit.display_data.entity0?.id}
-            allowNewEntity1={!edit.display_data.entity1?.id}
+            allowNewEntity0={relationship.entity0_id === 0}
+            allowNewEntity1={relationship.entity1_id === 0}
             relationship={relationship}
           />
         </td>

root/types/edit_types.js

@@ -259,8 +259,6 @@ declare type AddPlaceEditT = $ReadOnly<{
 declare type AddRelationshipEditT = $ReadOnly<{
   ...GenericEditT,
   +display_data: {
-    +entity0?: CoreEntityT,
-    +entity1?: CoreEntityT,
     +relationship: RelationshipT,
     +unknown_attributes: boolean,
   },