ci: docker deployment

[KyleTryon]

This change updates the CircleCI config to include separate testing and newly added docker building and deployment. The image will be published when a tag is pushed to both latest and the pushed tag.

Consideration: This will require a Dockerhub username and password. Ideally, this should be added as a Context and referenced in the workflow.

[KyleTryon]

Create a https://circleci.com/docs/contexts/ context with the Dockerhub login and password.

Required:

• DOCKER_PASSWORD
• DOCKER_USERNAME

Suggested change

	requires:
	context: [docker-deploy]
	requires:

In this configuration, this job will not run on pull requests, as contexts will only run when triggered by org users for security.

If you would like, I could split the docker build/test job and docker deploy job. In that situation, we will build and test the docker image on every commit and only deploy on tag. This is more correct but will use a bit more credits.

[KyleTryon]

Hey @jacebrowning, any comments for this?

[jacebrowning]

@KyleTryon thanks for adding this! I don't plan to publish Docker images for this project at this time but validating the Docker builds looks great! Perhaps you could update this so docker push is skipped when credentials are missing?