Add Safwan as 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.

Summary

@Saahmed has been with GitLab for 2 years, initially with groupremote development and now with groupcode review He has been working towards his backend maintainership, with @ck3g as his mentor.

• Authored 100+ merged MRs
• Reviewd 100+ merged MRs

Key Trainee Maintainer Reviews:

• Internal events for merge requests by vulnerability resolution workflow - Pointed out missing includes, which could be alright in local, but cause issues in production. Started a discussion about code coupling and the possibility of decoupling domains to maintain code quality
• Use Rust-based parser for tasklist parsing - An area of GitLab that you do not come across daily (at least in my case). I asked questions to better understand the domain and followed up with backwards compatibility concerns.
• Tidy up auto-merge quick action copy - I pointed out that we did not cover all automerge strategies, which could cause nil results, and recommended adding a failing spec as a regression guard if an author adds a new auto-merge strategy, but does not update quick actions
• Add details of NamespaceClusterAgentMapping in its delete mutation - Commentary on spec hygeine and ruby conventions
• Expose supported conversion types for a given work item type - Asked to mark new GraphQL endpoints as experimental, to prevent issues with breaking change policies.
• Remove the filters from the group's subgroup and project count fields - MR modified the way counts were displayed. Implementation LGTM, my only concern was that this could be a breaking change. We deferred to the backend maintainer to reach a consensus
• Refactor diff type selection logic - The MR is a refactor to support follow-up work on streaming diffs. I had questions as to why we were switching to the target project for diffs in this revision, which the author explained is actually the correct approach.
• Fix MergeRequestsFinder commit filtering for ge... (gitlab-org/gitlab!206264 - merged) - pointed out possible performance hiccups when not using indexes properly in filtering MR searches and possibilities of returning MRs not part of the passed filter criteria.
• Add Workspace Suspension with Delayed Termination - I identified a refactor that changed the default value of a field and pointed it out to the author, leading to follow-up action items being created.
• Return early in MergeRequestDiff#ensure_commit_shas

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 specialty 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. Review the additional guidelines for BE maintainers
8. Keep reviewing, start merging 🤘 😎 🤘