Fix: Align domain contact duplication logic and notifications

This commit refines the contact duplication checks and notification messages for domain creation and updates, ensuring consistency and addressing a bug in domain updates.

**Key Changes:**

*   **Consistent Duplicate Contact Handling:**
    *   The `check_for_cross_role_duplicates`, `remove_duplicate_contacts`, and `duplicate_contact?` methods are now more closely aligned between `DomainCreate` and `DomainUpdate` interactors.
    *   `DomainUpdate` now correctly uses `admin_contact_ids=` and `tech_contact_ids=` to assign filtered contacts. This resolves a `PG::UniqueViolation` error that occurred when trying to re-associate existing contacts using `_attributes=` methods.
    *   The `duplicate_contact?` method in `DomainCreate` was updated to match `DomainUpdate`, primarily checking for semantic duplicates based on attributes (name, ident, email, phone) rather than also including a `contact.code` check, which is more suitable for cross-role duplication.

*   **Standardized Notification Messages:**
    *   The `notify_about_removed_duplicates` method in both interactors now generates a more concise message: ". [Role] contact [CODE] was discarded as duplicate;" for each discarded contact.
    *   This message is appended to `domain.skipped_domain_contacts_validation`.

*   **EPP & REPP Response Updates:**
    *   The `message` method in `Repp::V1::DomainsController` now correctly appends `domain.skipped_domain_contacts_validation` to the "Command completed successfully" message, ensuring it appears in REPP JSON responses for both create and update.
    *   The EPP XML views (`app/views/epp/domains/create.xml.builder` and `app/views/epp/domains/success.xml.builder`) are updated to dynamically include `domain.skipped_domain_contacts_validation` in the `<msg>` tag.

*   **Model Attribute:**
    *   Added `skipped_domain_contacts_validation` as a string attribute to the `Domain` model to store these notification messages.

*   **Test Refinements (Implicit):**
    *   The related test suite for domain updates (`test/integration/epp/domain/base_test.rb`) was being updated to reflect these logic changes and assert the correct notification messages.

These changes improve the robustness and consistency of contact management during domain operations, providing clearer feedback to users about discarded duplicate contacts.

app/controllers/repp/v1/domains_controller.rb

@@ -80,7 +80,7 @@ module Repp
         handle_errors(@domain) and return unless action.call
         # rubocop:enable Style/AndOr
 
-        render_success(data: { domain: { name: @domain.name,
+        render_success(message: message, data: { domain: { name: @domain.name,
                                          transfer_code: @domain.transfer_code,
                                          id: @domain.reload.uuid } })
       end
@@ -104,7 +104,7 @@ module Repp
           return
         end
 
-        render_success(data: { domain: { name: @domain.name } })
+        render_success(message: message, data: { domain: { name: @domain.name } })
       end
 
       api :GET, '/repp/v1/domains/:domain_name/transfer_info'
@@ -239,6 +239,10 @@ module Repp
         index_params[:offset] || 0
       end
 
+      def message
+        "Command completed successfully#{@domain.skipped_domain_contacts_validation if @domain.skipped_domain_contacts_validation.present?}"
+      end
+
       def index_params
         params.permit(:limit, :offset, :details, :simple, :q,
                       q: %i[s name_matches registrant_code_eq contacts_ident_eq