Island: Add /api/request-otp endpoint

[cakekoa]

What does this PR do?

Fixes part of #3076.

Adds mock endpoint for requesting OTP

PR Checklist

• Have you added an explanation of what your changes do and why you'd like to include them?
• Is the TravisCI build passing?
• Was the CHANGELOG.md updated to reflect the changes?
• Was the documentation framework updated to reflect the changes?
• Have you checked that you haven't introduced any duplicate code?

Testing Checklist

• Added relevant unit tests?
• Have you successfully tested your changes locally? Elaborate:

  Tested by {Running the Monkey locally with relevant config/running Island/...}

• If applicable, add screenshots or log transcripts of the feature working

[mssalvatore]

Could we base this off of 2157-consolidate-authentication-service-logic (which will probably get merged tomorrow? This will lead to less rework/conflict resolution than the other way around.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +0.01 🎉

Comparison is base (34d06df) 67.56% compared to head (3b184e5) 67.58%.

❗ Current head 3b184e5 differs from pull request most recent head a25ac6c. Consider uploading reports for the commit a25ac6c to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3083      +/-   ##
===========================================
+ Coverage    67.56%   67.58%   +0.01%     
===========================================
  Files          443      444       +1     
  Lines        12720    12730      +10     
===========================================
+ Hits          8594     8603       +9     
- Misses        4126     4127       +1     

see 4 files with indirect coverage changes

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[mssalvatore]

After much discussion, we settled on GET /api/agent-otp and POST /api/agent-otp-login.