[DEVOPS-123] Added optional ability to perform supported image versions checks.

[barbun]

Description

Currently, PaaS customers have the ability to use unsupported image versions. This can introduce issues when an unsupported version of an image is being used (eg. PHP 7, when the last supported version is 8).

Proposed solution

Extend docker-base-image check to allow optional version constrain within the allowed list, which will reject builds that do not adhere to the specified image version constraint.

If the version constraint is added to the image, then that version will be considered the last supported version, meaning that images with lower version will not pass validation.

For version comparison it is proposed to use https://github.com/hashicorp/go-version that follows SemVer

Usage

The version constraint can be added either with : or @ suffix tag. When no version suffix is specified then any version will pass the validation (current behaviour)

docker-base-image:
    - name: '[FILE] Allowed image lookup'
      paths:
        - ./
      allowed:
        - govcms/nginx-drupal:9.5.3
        - uselagoon/varnish-drupal@latest

[steveworley]

Minor change on the function name so that it better represents what the function is doing.

[steveworley]

LGTM

[yusufhm]

LGTM