WIP: Resolve "Follow-up: show warning when adding user to group that incur a charge"

What does this MR do?

When a user is invited or a group is invited then the user is check if the user is already occupying the paid seat or not and if it does occupy then render a modal popup with confirm button sending the same action with confirm=true as the params.

This confirm true will add the user even they taking up extra seat or not.

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

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

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• 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

Closes #202325 (closed)