Disable Remove Group Button for Group with Subscription

What does this MR do?

Prevent deletion of groups with a paid gitlab.com subscription.

This prevents data integrity issues with CustomersDot that occur when a group is deleted while linked with a subscription. More details are in the issue.

Issue: customers-gitlab-com#1879 (closed)

Screenshots

A Premium subscription group with delayed deletes enabled cannot be deleted

A Bronze subscription group cannot be deleted

A subgroup of a Premium subscription group can be deleted

A subgroup of a Bronze subscription can be deleted

The link in the info text block links to the documentation

If the user somehow bypasses the button to force a delete, the backend prevents this:

If the user used the Chrome dev tools to enable the button, for instance.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
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• Documentation (if required)
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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

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• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team