Create GitHub Action to build and push docker image from mud repository

[nswarner]

May require a new AWS IAM user token specifically meant for managing pushes to ECR from GitHub Actions (separate from website repository pushes to S3). Likely single user in AWS IAM with secrets stored at the GitHub organization level (to be used with all mud repository GitHub Actions).

On commit push,

• [x] GitHub action should launch centos7 container (build environment)
• [x] Build environment should authenticate via AWS API Tokens in secrets to AWS ECR
• [x] Build environment should run docker build -t <mud>:<versioning> .
• [x] Build environment should push the resulting docker image to ECR

Required work to connect,

• [x] Create a new AWS IAM User purpose-built for GitHub Actions pushes to ECR
• [x] Create a new AWS IAM group+policy for new IAM User, allow minimal permissions to push to ECR
• [x] Create API tokens for new AWS IAM User
• [x] Store API tokens in MudMuseum GitHub organization

Deciding on versioning schema,

• [x] Review StackOverflow reference to GitHub Actions run-id and run-number
• [x] Understand ECR lifecycle policies, how to automatically destroy old image versions

References:

• https://stackoverflow.com/questions/54310050/how-to-version-build-artifacts-using-github-actions
• https://docs.github.com/en/actions/reference/context-and-expression-syntax-for-github-actions#github-context

[nswarner]

Likely overlap with #19.

[nswarner]

Created Action, works as expected with exception. Intended to run on ARM64 architecture, but default GitHub Runner for ubuntu-latest is not ARM64. Looking into cross-compiling.. If cross compiling doesn't work, I may move the organization onto AWS CodeCommit / CodeBuild / Code*... rather than GitHub+GitHub Actions.

[nswarner]

Converted from t4g.micro to t3a.micro. Cost change of ~$10 on a reserved instance spread over 3 years (effective change of ~$0.28/month). Considerations show benchmark performance loss on CPU with change of ~5-40%.

[nswarner]

Conversion to t3a.micro allows GitHub Actions build to run on x86_64 architecture, which aligns artifact build architecture with architecture of server that runs artifact.

[nswarner]

Functioning as intended.