Make WorkPackage factory use default factory for type if one is defined

With TestProf, it's possible to define a default factory for a given
factory using `FactoryBot.set_factory_default`. It activates if a
factory is set for a given field, for instance `author factory: :user`.

For work packages, there is no such factory defined for `type` field
because we have a `after_build` hook to use the first project's type.
Nevertheless, when a default factory has been set, we want to use it
instead, especially as getting the first type is not deterministic when
there are multiple types defined.

This commit makes the WorkPackage factory use this factory default for
the `type` field if one is defined.

This fixes flaky test `spec/services/relations/delete_service_spec.rb`
where the wrong type would be used instead of the intended one. I also
updated the position of the type with mandatory custom field to be after
the type task so that it would work even without the default factory.

spec/factories/work_package_factory.rb

@@ -74,7 +74,7 @@
     end
 
     callback(:after_build) do |work_package, evaluator|
-      work_package.type = work_package.project.types.first unless work_package.type
+      work_package.type ||= TestProf::FactoryBot.get_factory_default(:type) || work_package.project.types.first
 
       custom_values = evaluator.custom_values || {}
 

spec/services/relations/delete_service_spec.rb

@@ -39,6 +39,7 @@
   shared_let(:type_task) { create(:type_task, :default) }
   shared_let(:type_with_mandatory_cf) do
     create(:type,
+           position: type_task.position + 1,
            name: "Type with mandatory custom field",
            custom_fields: [mandatory_custom_field])
   end