Adding an optional version env var for the version endpoint to return

[alexcottner]

No description provided.

[willkg]

Why add this additional source of information instead of using the version.json file?

[alexcottner]

We adjusted the remote-settings release process to re-tag the existing image instead of building a fresh one (link). This reduces our release times and allows us to use the exact same image that's been working great already in dev/stage.

But, the version file doesn't then get rebuilt so our version endpoint is incorrect. My best ideas to solve this were:

1. Allow for an optional version parameter to be sent (this PR basically)
2. Update and mount a configmap for the version.json file on deploy

This felt a little easier to me but I'm open to option 2.

[willkg]

I think sliding the version in outside of the version.json file doesn't make sense and breaks the contract of version.json.

I think it'd be better to have a short Dockerfile template, expand the template with the image details of the stage image you're using, and then COPY the updated version.json file.

You should talk with @grahamalama and see if that's something we can put in deploy-actions.

[alexcottner]

🤔 Yeah that's another option and is pretty simple to implement

[willkg]

This library uses pytest, so you should use its monkeypatching:

https://docs.pytest.org/en/stable/how-to/monkeypatch.html

Suggested change

	def test_env_var_override(tmpdir):
	content = {"spam": "eggs"}
	mock.patch.dict(os.environ, { "DOCKERFLOW_VERSION": "foo"})
	version_json = tmpdir.join("version.json")
	def test_env_var_override(tmpdir, monkeypatch):
	content = {"spam": "eggs"}
	monkeypatch.setenv("DOCKERFLOW_VERSION", "foo")
	version_json = tmpdir.join("version.json")