437 user search

[TheAndrewJackson]

Purpose

Make it possible for the admin ui to search for users by username.

Changes

• Add username query parameter to the get_users function that allows for filtering by username

Checklist

• Applicable documentation updated (guides, quickstart, postman collections, tutorial, fidesdemo, database diagram.
• If docs updated (select one):
  • documentation complete, or draft/outline provided (tag docs-team to complete/review on this branch)
  • documentation issue created (tag docs-team to complete issue separately)
• Good unit test/integration test coverage
• This PR contains a DB migration. If checked, the reviewer should confirm with the author that the down_revision correctly references the previous migration before merging
• The Run Unsafe PR Checks label has been applied, and checks have passed, if this PR touches any external services

Ticket

Fixes #437

[adamsachs]

looks good to me!