Enable PR Status Notifications

[kneehill]

Description

✅ Adds a basic PR template to fill out that describes what changes are being committed to the repo,

✅ Adds a new custom action post-to-slack that is used to streamline notification handling,

✅ Adds a new workflow, notify-pr-status.yml, that triggers whenever a PR is opened (not drafted), approved, or merged that then calls the post-to-slack action which sends the relevant notification through Slack to #delivery-practice-cato that includes the PR name, PR author & a call to action to review the PR with a link to referenced PR,

✅ Adds new repo scoped variable (SLACK_CHANNEL_ID) and secret (SLACK_BOT_TOKEN) and configures automated Slack notifications that @mention a new Slack user group setup named @cato-repo-pr-approvers for notifying approvers of the relevant call-to-action,

✅ Adds a CODEOWNERS file to the repo and configures the repo's branch merge strategy to now enforce the requirement that a listed CODEOWNER in the new cato-repo-pr-approvers GitHub team approves all pull requests to the main branch to ensure proper validation before acceptance,

✅ Adds pre-commit configuration and markdown linting rules,

❌ Removes the smaller secrel.png image from the repo as well as a larger SecRel.png image & re-adds only one copy of the higher resolution image to the repo in order to correct OS case-insensitive file system issues detected when cloning the repo on MacOS,

❌ Removes old references to the smaller secrel.png image and ensures the higher resolution image is instead referenced.

Slack notifications tests for review:

• A PR was opened in the repository:

• A PR was approved in the repository:

• A PR was merged to the main branch of the repository:

Type of change(s)

• New feature(s) 🎉 (non-breaking change(s) that add functionality)
• Bug fix(s) 🐛 (non-breaking change(s) which fix an issue(s)