Support editing of deployment approval rules in project level protected environments settings UI
## Release notes
With this release, we have updated the configuration experience for deploy approvals. Now, the settings UI defaults to the more flexible multiple approval rules engine, instead of unified approval rules. We are moving to this new model because it is more flexible and lets teams define with more clarity, who can execute a deployment vs who can approve it right in the settings UI. Teams can still use the API for changing existing deploy approval configurations if needed.
## Problem
We have had API-basis support for [multiple approval rules](https://docs.gitlab.com/ee/ci/environments/deployment_approvals.html#multiple-approval-rules) implemented in gitlab#345678, but similar to gitlab#362236 and gitlab#355708, we still need to extend that feature to the frontend part, so that users can interact more easily with multiple approval rules in project-level protected environment settings UI.
Currently, the settings UI for [Protected Environments](https://docs.gitlab.com/ee/ci/environments/protected_environments.html) only displays [unified approval settings](https://docs.gitlab.com/ee/ci/environments/deployment_approvals.html#unified-approval-setting) for a specific environment as shown :point_down_tone2:

It does not display the correct amount of required approvals (if only multiple approvals rules are used, the amount will be zero despite each rule having a required approvals count). Additionally, there's no listing of approval rules and their associated **access level**, **group**, or **project**.
## Proposal
Update the frontend part to support editing deployment approval rules in the project-level protected environments settings UI.
Such that each executor rule will be displayed, along with its associated:
- Access Level
- Group
- Project
- Required Approvals
| Proposed Flow |
|---------------|
|  |
## 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
**Flow after banner (+1 milestone in the future):**
* Full UX Flow with details can be found [here](https://gitlab.com/gitlab-org/gitlab/-/issues/367700/designs/UX_Flow_-_Protected_Environment_Settings__No_Environments_Protected_.png).
* Provide users with help text on how to use unified approval rules.
* Note: If a user is selected for an approval rule, we lock the amount of approvals to 1.
| Settings Page | Environment Selected | Approvers/Executors Selected |
|---------------|----------------------|------------------------------|
|  |  |  |
## [Figma File](https://www.figma.com/file/Khc6SllbMl78afplkQ27TB/Support-multiple-approval-rules-in-project-level-protected-environments-settings-UI?node-id=67%3A29862)
#### Protected environment UI:
* Full UX Flow with details can be found [here](https://gitlab.com/gitlab-org/gitlab/-/issues/367700/designs/UX_Flow_-_Protected_Environment_Settings__Protected_Environments_.png).
| Collapsed | Expanded | Modals |
|-----------|----------|--------|
|  |  |  |
## Technical Proposal
1. Update [main edit component](https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/app/assets/javascripts/protected_environments/protected_environment_edit.vue) to handle deployment executor rules
1. Use components shared between this issue and #378446 to implement new form, ideally completely reusable with only inputs for rule type to change behaviour
1. Interact with the [protected environment public API](https://docs.gitlab.com/ee/api/protected_environments.html#example-update-an-approval_rule-record) to handle updating and deleting of rules
* will likely need to update `api.js` to handle basic interaction
1. fetch group and user information via `api.js`. The required functions should already be in place.
All should be behind a feature flag, `protected_environments_multiple_rules_setting_ui`. If this flag hasn't been created yet, [please do](https://docs.gitlab.com/ee/development/feature_flags/#feature-flags-in-the-development-of-gitlab) and attach the flag rollout to &9042
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