fix(jsonapi): exit loop when relationship class is found

[GwendolenLynch]

Q	A
Branch?	main
License	MIT

When using the model I describe in #6212 (comment), the $className variable is overwritten by null when an additional (3rd +) type is in the union.

[soyuka]

shouldn't we use all the types? I mean in your example it should be one of Species (ref/iri), null, int right?

[GwendolenLynch]

Fair call. Updated.

[soyuka]

Do you think you can add a test? I usually add a fixture then uses the JsonSchemaGenerateCommandTest to add a functional test

[GwendolenLynch]

Tests added. The core remaining issue remaining in #6212 isn't in the schema factory so I just extended the tests I added in #6223.

[soyuka]

nice thanks!