Add PR deployment preview

New Feature / Enhancement Checklist

• I am not disclosing a vulnerability.
• I am not just asking a question.
• I have searched through existing issues.

Current Limitation

Reviewing a dashboard PR requires more effort than PRs from other repos because

• Parse Dashboard is a visual product with UI
• We don't have UI testing as part of the CI

The dashboard PR has to be cloned locally in a development environment to see the effect of most PRs.

Feature / Enhancement Description

Add a preview deployment to easily review and preview PRs online without having to clone the PR locally.

See https://docs.uffizzi.com/references/uffizzi-ci/#2-install-authorize-the-uffizzi-github-app

Example Use Case

n/a

Alternatives / Workarounds

Clone locally.

3rd Party References

n/a

Uffizzi Feedback

• There seems to be an URL issue, see https://github.com/parse-community/parse-dashboard/pull/2370#issuecomment-1406928232:

  https://https://app.uffizzi.com/projects/5259/deployments

• It would be nice to have all files in a .uffizzi directory. Currently we have:

  ./docker-compose.uffizzi.yml
  ./nginx-uffizzi/...
  

• When Uffizzi adds a comment it should probably delete any existing Uffizzi comments, otherwise the thread gets full of comments, and these comments are quite long.

• While deploying a new commit, the preview URL shows an nginx error page; it's unclear whether the deployment / PR has an issue; it would be better to show a "deployment is progress" page
  

Start with docker-compose.uffizzi.yml and the nginx-uffizzi/ directory, then review the Uffizzi CI integration referenced in the issue and the feedback from PR 2370. Done means pull requests receive usable online previews, the deployment URL is correct, deployment progress is understandable, and repeated Uffizzi comments do not unnecessarily fill the thread.