fix: Prevent uniqueness validation error when updating case contact types

Fixes Bugsnag error "Validation failed: Case contact has already been taken"
(Error URL: https://api.bugsnag.com/projects/5f370b68136a4b0010d15364/events/6924fd6f015b929d46570000)

The issue occurred when updating case contacts with contact types. The
remove_unwanted_contact_types method used contact_types.clear which marks
records for deletion in memory but doesn't immediately execute DELETE
statements. When the subsequent update attempted to create new join records,
the old records still existed in the database, triggering the uniqueness
validation on CaseContactContactType.

Changed to use destroy_all which immediately deletes records from the
database, ensuring old contact type associations are fully removed before
new ones are created.

Added regression test to prevent this issue from recurring.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: compwron

app/controllers/case_contacts/form_controller.rb

@@ -165,7 +165,7 @@ def case_contact_params
   # Deletes the current associations (from the join table) only if the submitted form body has the parameters for
   # the contact_type ids.
   def remove_unwanted_contact_types
-    @case_contact.contact_types.clear if params.dig(:case_contact, :contact_type_ids)
+    @case_contact.case_contact_contact_types.destroy_all if params.dig(:case_contact, :contact_type_ids)
   end
 
   def remove_nil_draft_ids

spec/requests/case_contacts/form_spec.rb

@@ -234,6 +234,19 @@
         case_contact.reload
         expect(case_contact.contact_type_ids).to contain_exactly(contact_types.first.id)
       end
+
+      it "allows re-assigning the same contact type without uniqueness validation error" do
+        # This test prevents regression of Bugsnag error:
+        # "Validation failed: Case contact has already been taken"
+        case_contact.update!(contact_type_ids: [contact_types.first.id])
+        expect(case_contact.contact_type_ids).to contain_exactly(contact_types.first.id)
+
+        # Re-submit form with same contact type (simulates user editing and saving)
+        request
+
+        case_contact.reload
+        expect(case_contact.contact_type_ids).to contain_exactly(contact_types.first.id)
+      end
     end
 
     context "when contact topic answers in params" do