Make Igor Drozdov (@igor.drozdov) a backend maintainer

Trainee maintainer issue: #4978 (closed)

• Worked at GitLab since Jan 2019 (13 months) within devopscreate and groupsource code
• Authored at least 131 merge requests
• Reviewed at least 40 merge requests during 7 months of my maintainership training and the last 2-3 months I've received no or minor post-review comments.

I believe, that my reviewing skills have improved during the training: I've become more attentive to details and learned which details to pay attention to. I think I'm ready to help with merging backend changes to GitLab project:

• Tend to give a detailed explanation for the proposed changes: gitlab-org/gitlab-foss!32472 (comment 214419899)
• Care about our test suite (gitlab-org/gitlab!22479 (comment 274499434)) and its performance (gitlab-org/gitlab!20825 (comment 253336943))
• Built an intuition of detecting the cases when extra help from a domain expert would be useful (gitlab-org/gitlab!22522 (comment 284257417)), which should help me in future seek expertise from a more experienced maintainer if necessary and learn from them in the process
• Maintainer of gitlab-shell and already merged some MRs i.e familiar with the responsibility of clicking the green Merge button which used to be disabled before

@gitlab-org/maintainers/rails-backend what do you think?