Add Moaz Khalifa as a backend maintainer

Manager Justification

It's hard to specify hard requirements for becoming a maintainer, which is why the documentation consists of flexible guidelines. Reviewers are encouraged to think of their eligibility for maintainership in the terms of "I could be ready at any time to be a maintainer as long as my work as an author and reviewer is consistent with other maintainers".

• The MRs reviewed by the candidate consistently make it through maintainer review without significant additionally required changes.
• The MRs authored by the candidate consistently make it through reviewer and maintainer review without significant required changes.

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• Trainee Maintainer Log: https://gitlab.com/gitlab-com/www-gitlab-com/-/issues/34959+s
• Reviewed 328 MRs against gitlab-org/gitlab since joining GitLab (list)
  • Some highlights:
    • Allow relation tree restorer to import single r... (gitlab-org/gitlab!147913 - merged) • James Nutt • 16.11 - suggested some code simplification, validation reordering for better performance, more descriptive error messages, and performance improvements including suggesting hash lookups over array searches for better efficiency (details)
    • Epics Roadmap: Add hasChildrenWithinTimeframe f... (gitlab-org/gitlab!151917 - merged) • Joseph Wambua • 17.1 - identified N+1 query issues in the initial implementation and suggested a more efficient approach using Gitlab::Graphql::Aggregations::Epics::LazyEpicAggregate to avoid additional database queries while reusing existing epic metadata loading mechanisms (details)
    • Allow exceptions to "Allow duplicates" group se... (gitlab-org/gitlab!165467 - merged) • Radamanthus Batnag • 17.7 - suggested centralizing the duplicate checking logic in Namespace::PackageSetting.duplicates_allowed? rather than modifying each individual service, which simplified the code and reduce duplication across package formats (details)
    • Clean up Conan objects when deleting package file (gitlab-org/gitlab!189175 - merged) • Océane Legrand • 18.1 - provided feedback on code organization (suggested a DRY approach with a new PackageFileable concern), performance optimization (recommended limiting ~database queries to only Conan files), and test improvements
    • Introduce Packages::TerraformModule::PackagePre... (gitlab-org/gitlab!196116 - merged) • Dzmitry (Dima) Meshcharakou • 18.3 - identified a potential N+1 query performance issue with suggestions for preloading associations, noted a typo in test descriptions, and recommended various code improvements including better association preloading and test structure optimizations.
• Authored 235 merged MRs against the gitlab-org/gitlab project (list)
  • Some highlights:
    • Add support for npm deprecate (gitlab-org/gitlab!117009 - merged) • Moaz Khalifa • 16.0
    • Support NuGet version normalization (gitlab-org/gitlab!121260 - merged) • Moaz Khalifa • 16.3
    • Support dotnet nuget api-key option (gitlab-org/gitlab!121564 - merged) • Moaz Khalifa • 16.1
    • Add custom nuget version sorter (gitlab-org/gitlab!122484 - merged) • Moaz Khalifa • 16.1
    • Add service to handle disallowing duplicate NuG... (gitlab-org/gitlab!128269 - merged) • Moaz Khalifa • 16.4

Before Merging (Manager Tasks)

• Close any relevant trainee maintainer issues with a comment indicating that this merge request is being created, as (they are no longer required to become a maintainer).
• Mention the maintainers from the given speciality with the template below and ask them to provide feedback to the manager directly. Emphasize that any negative feedback should be communicated privately to the manager/mentor, not in the merge request, as outlined in our maintainership feedback documentation.
• Leave this merge request open for 1 week, to give the maintainers time to provide feedback.
• Check this box to confirm that you approve the access provision.
• Ensure we have at least 2 approvals from existing maintainers.

Template call to action

SPECIALITY Maintainers, please review this proposal to make TRAINEE maintainer of PROJECT.

* If you have blocking feedback adhering [to the documentation](https://handbook.gitlab.com/handbook/engineering/workflow/code-review/#request-maintainership-feedback) please share it with me privately.
* If you are in agreement, and can vouch for this proposal, please approve.

After 1 week, if there is no blocking feedback and at least 2 approvals, I will merge this MR.

Once This MR is Merged

1. Join the #backend_maintainers Slack channel
2. Remove yourself from maintainer_mentorship.yml and consider adding yourself as a maintainer mentor.
3. Ask the maintainers in your group to invite you to any maintainer-specific meeting, if one exists.
4. Let a maintainer add you to <project>/maintainers/backend with Owner access level.
5. Announce it everywhere
6. Familiarize yourself with documentation for Merging a merge request
7. Keep reviewing, start merging 🤘 😎 🤘