[lib][web][native] Use real admin username or id when adding a ks

Summary:
This was a part of my patch diff D11141, but actually it would make sense to already land this
This partially addresses ENG-6298, becuse if someone is set up with identity, then the real username will be used

Test Plan: Added a keyserver on native, and checked that the keyserver shows up on the list of keyservers with username keyserver<id>

Reviewers: tomek, michal, ginsu

Reviewed By: ginsu

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11283