[E2E] Add new test for Custom Server Hooks on Create Tag API Endpoint

Description of the test

This is an API level test to ensure that the ability to define Custom Server Hook errors messages https://docs.gitlab.com/ee/administration/server_hooks.html#custom-error-messages is being respected.

This is part of an effort to avoid future regression in this space as part of #362666 (closed)

NB - The use of the tag API endpoint in this scenario is somewhat arbitrary as many events can trigger a prereceive hook but it's not feasible for now to test this scenario for every single action that may trigger such an event.

New Test Case: https://gitlab.com/gitlab-org/gitlab/-/quality/test_cases/369053

Checklist

• Confirm the test has a testcase: tag linking to an existing test case in the test case project.
• Note if the test is intended to run in specific scenarios. If a scenario is new, add a link to the MR that adds the new scenario.
• Follow the end-to-end tests style guide and best practices.
• Use the appropriate RSpec metadata tag(s).
• Most resources will be cleaned up via the general cleanup task. Check that is successful, or ensure resources are cleaned up in the test:
  • New resources have api_get_path and api_delete_path implemented if possible.
  • If any resource cannot be deleted in the general delete task, make sure it is ignored.
  • If any resource cannot be deleted in the general delete task, remove it in the test (e.g., in an after block).
• Ensure that no transient bugs are hidden accidentally due to the usage of waits and reloads.
• Verify the tags to ensure it runs on the desired test environments.
• If this MR has a dependency on another MR, such as a GitLab QA MR, specify the order in which the MRs should be merged.
• (If applicable) Create a follow-up issue to document the special setup necessary to run the test: ISSUE_LINK
• If the test requires an admin's personal access token, ensure that the test passes on your local environment with and without the GITLAB_QA_ADMIN_ACCESS_TOKEN provided.