WIP: Add leave link to member_access_granted email

What does this MR do?

• Add leave link to member_access_granted email

• Add url helper methods for leave actions (leave_project_members_url/leave_group_members_url)

• Allow GET requests to leave actions

• Add email_token to auth protected endpoints for one-click email actions

Clicking/visiting the leave link will perform the leave action and direct the user to their dashboard with a flash notice.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/59421

How can I preview the email?

Visit: http://localhost:3001/rails/mailers/notify/member_access_granted_email.html

https://docs.gitlab.com/ee/development/emails.html#mailer-previews

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance 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

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