Add GET `/users` endpoint

[slifty]

This PR adds a new /users endpoint which will allow the front end to look up the id associated with their session.

I decided to implement this with auth context awareness off the bat, which means administrative users can actually view ALL users in the system if they want.

Resolves #942

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 83.33333% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 88.30%. Comparing base (b23b8a6) to head (8cb2d14).

:exclamation: Current head 8cb2d14 differs from pull request most recent head d2c3c13. Consider uploading reports for the commit d2c3c13 to get more accurate results

Files	Patch %	Lines
src/handlers/usersHandlers.ts	68.18%	6 Missing and 1 partial :warning:
...eryParameters/extractAuthenticationIdParameters.ts	83.33%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #946 +/- ## ========================================== - Coverage 88.48% 88.30% -0.18% ========================================== Files 119 123 +4 Lines 1650 1702 +52 Branches 206 210 +4 ========================================== + Hits 1460 1503 +43 - Misses 175 183 +8 - Partials 15 16 +1 ```

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[slifty]

I think all of the untested lines are of the category of "it's OK not to test them"

[hminsky2002]

Verifying success on all of the same checks as @reefdog. Hitting approve!