Make sashi_kumar 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.

Sashi joined GitLab 2 years ago and was a community contributor before that for more than a year and having recognized as MVP twice (13.0, 13.6). Sashi already reviewed 341 MRs and authored 108 MRs including 8 (8%) contributions outside his group's main category. Although the process to become maintainer he has followed trainee process to gather feedback and improve his reviews.

When reviewing code and when necessary, Sashi tags domain experts for a second opinion. He follows guidelines and uses Conventional Comment format to communicate his intentions.

His contributions to general improvement include:

• reusing existing code,
• confirming test coverage,
• providing statistics for changes and proposing simplicity to avoid over optimization,
• verifying if any database change does not impact the degrade the performance or correctness,
• suggesting improvements to background migration to improve the execution time,
• ensuring the guidelines are followed by linking them during reviews.

Before Merging (Manager Tasks)

• Mention the maintainers from the given specialty and ask them to provide feedback to the manager directly.
• Leave this merge request open for 1 week, to give the maintainers time to provide feedback.
• Ensure we have at least 2 approvals from existing maintainers.

Once This MR is Merged

1. Create an access request for maintainer access to gitlab-org/gitlab.
2. Join the backend-maintainers slack group
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 @gitlab-org/maintainers/rails-backend
5. Announce it everywhere
6. Keep reviewing, start merging 🤘 😎 🤘