Short fix for the morph case.
Was missing the logic for the joinColumnName: we need to add the
"ObjcectMetadataName" on top the the "FieldMetadataName" for morph
relation like it was designed on fieldmetadata service.
On the typescirpt side: the "as FieldMetadataRelationSettings" is not
ideal but I inherit from the a as FieldMetadataInterface type that does
not know the as FieldMetadataType from its parent. If you have a better
simple idea, let me know.
Note : I think we could refactor a bit this part later on.
37d7996a04