Add deployment approval comment field

What does this MR do and why?

A comment field allows users to describe why a deployment is approved or rejected.

It shows a count of remaining characters. The count turns orange when 30 or less are left, and turns red once the comment is over the limit.

This counter should be added to GitLab UI (and made pajamas compliant), but is good here for now.

Changelog: added

Screenshots or screen recordings

Screencast_2022-03-11_15_53_19

How to set up and validate locally

1. Then add the following .gitlab-ci.yml to a project for some deployments:

stages:
    - deploy
    - stop
image: alpine:latest

deploy-prod:
    stage: deploy
    script:
        - sleep 6000
        - echo "deploying prod"
    environment:
        name: production

deploy-staging:
    stage: deploy
    script:
        - echo "deploying staging"
    environment:
        name: staging
        url: https://example.com
    when: manual

deploy-review:
    stage: deploy
    script:
        - echo "Deploying review/$CI_COMMIT_REF_NAME"
    environment:
        name: review/$CI_COMMIT_REF_NAME
        auto_stop_in: 1 week
    only:
        - branches
    except:
        - main


stop_review_app:
  script: stop-review-app
  stage: stop
  environment:
    name: review/$CI_COMMIT_REF_SLUG
    action: stop
  rules:
    - if: $CI_MERGE_REQUEST_ID
      when: manual

Run a pipeline to create the initial environments, then protect the staging environment in Settings > CI/CD.

Run another pipeline, and check the environments page.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.