Merge branch 'benjaminking-verify-api' into 'master'

Add Pages domain verify API endpoint

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/174330



Merged-by: Piotr Skorupa <pskorupa@gitlab.com>
Approved-by: Marcin Sedlak-Jakubowski <msedlakjakubowski@gitlab.com>
Approved-by: Piotr Skorupa <pskorupa@gitlab.com>
Reviewed-by: Piotr Skorupa <pskorupa@gitlab.com>
Co-authored-by: Marcin Sedlak-Jakubowski <msedlakjakubowski@gitlab.com>
Co-authored-by: Ben King <bking@gitlab.com>