feature: ECR plugin

[niallthomson]

🔖 Feature description

Ability to view container images stored in ECR related to a given entity. This should be designed to display as an additional tab on the entity page (similar to CI/CD) and present a table of the image tags for a given ECR repository.

Annotations:

• aws.amazon.com/amazon-ecr-repository-arn to show a specific ECR repository
• aws.amazon.com/amazon-ecr-repository-tags to look up a set of ECR repositories based on tags

If the "tags" annotation is used and multiple repositories are returned then a dropdown menu should be presented to choose the repository to view, similar to the CodePipeline executions entity page.

Columns to display:

• imageTags (comma separated)
• imagePushedAt
• imageSizeInBytes (in Mb)
• imageDigest

🎤 Context

There are several existing Backstage plugins that provide information related to container registries:

https://github.com/BESTSELLER/backstage-plugin-harbor/blob/master/README.md
https://janus-idp.io/plugins/quay
https://janus-idp.io/plugins/jfrog-artifactory/

✌️ Possible Implementation

Look up the ARNs of the ECR repositories using the standard resource locator patterns.

Extract the repository name from each ARN and then use DescribeImagesCommand to retrieve summary information about the images in each repository.