Improve PR verification

[dkundel]

I think it would be nice to setup some E2E test to verify that everything works as part of the PR automation.

What I have in mind right now is to deploy using the example deploy script (maybe with some tweaks), then once it's deployed to a request against the endpoint to verify it deployed correctly. From there we could run a cleanup or we can keep it up.

[dkundel]

Seems like there is a limit of 25 environments per service. So maybe we create a new environment for each PR. And then depending on whether we think it's realistic that we'll have more than 25 PRs at a time open, either immediately remove that environment again or delete it on closing the PR

[philnash]

Linking to #152. There should be a decision which would be the best approach here.