Add username filtering for /users endpoint

Is your feature request related to a problem? Please describe.
Unless you already have a user's DoD Identification Number / EDI-PI, tracking down a user's account after initial creation is very tedious because you must manually sort through the full paginated response from the /users endpoint. The office parameter doesn't help because all users are under HQ by default.

Describe the solution you'd like
A query parameter such as username or like that allows wildcard-based filtering by username. This would allow searching by more easily-obtainable identifiers such as the user's first or last name. Could also be useful to allow filtering by roles per office (e.g. all users with CWMS Users in LRL) but this might be a little messier on the parameter-format side.

Describe alternatives you've considered
This could be a separate endpoint (e.g. /users/catalog), but seems like it fits under /users easily enough -- and feels more RESTful that way.

Additional context
n/a