Alert users that they can still make unified approval rules via the API

Problem

Once the settings UI for Protected Environments utilizes multiple approval rules, we need to alert users that they can still utilize unified approval rules, but by API only.

Proposal

Update the frontend to display an alert that users can still use the API to configure their unified approval rules

Designs:

Flow for protecting an environment:

Flow with Banner:

For one milestone after this launches, we provide users with a banner letting them know where unified approval rules went and more information about multiple approval rules. After this milestone passes, we remove the banner and move the information to the approval rules help text.

Banner

• API: https://docs.gitlab.com/ee/ci/environments/deployment_approvals.html#unified-approval-setting
• Multiple Approval Rules: https://docs.gitlab.com/ee/ci/environments/deployment_approvals.html#multiple-approval-rules

Technical Proposal

1. Pass links to multiple approval rules docs and API docs via the vue app mount point
2. Use the gitlab alert component to display the text and links
3. make sure the alert is dismissible, but we do not need to persist this dismissal to the backend. The alert should come back on page load

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