Set reply UUID

[heartsucker]

Status

Ready for review

Description of Changes

Fixes #3957

Allow API consumer to set the Reply.uuid in the request to allow clients to easily track in-flight message in their own cache/db.

Testing

make test TESTFILES=tests/test_journalist_api.py::test_set_reply_uuid

Also play with the api some?

Deployment

This is a non-breaking change to the API.

Checklist

If you made changes to the server application code:

• Linting (make ci-lint) and tests (make -C securedrop test) pass in the development container

[codecov-io]

Codecov Report

Merging #3958 into develop will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #3958      +/-   ##
===========================================
+ Coverage    84.62%   84.64%   +0.01%     
===========================================
  Files           43       43              
  Lines         2739     2754      +15     
  Branches       296      298       +2     
===========================================
+ Hits          2318     2331      +13     
- Misses         354      355       +1     
- Partials        67       68       +1

Impacted Files	Coverage Δ
securedrop/securedrop/journalist_app/api.py	94.89% <0%> (-0.69%)	⬇️

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[redshiftzero]

from visual review of the diff, lgtm - this just needs a doc update and then it's good to go