Add Action to DeploymentStatusEvent

[JoannaaKL]

In GH docs we can see that deployment_status has a field action, that is always set to created. This pr adds it to json representation.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.89%. Comparing base (2b8c7fa) to head (88abac8).
Report is 52 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3163      +/-   ##
==========================================
- Coverage   97.72%   92.89%   -4.83%     
==========================================
  Files         153      171      +18     
  Lines       13390    11476    -1914     
==========================================
- Hits        13085    10661    -2424     
- Misses        215      724     +509     
- Partials       90       91       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[gmlewis]

Thank you, @JoannaaKL !
LGTM.
Merging.