Merge branch 'djadmin-dast-additional-variables-4' into 'master'

Add support for "option variables" in GraphQL mutation

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/174541



Merged-by: Miranda Fluharty <mfluharty@gitlab.com>
Approved-by: Miranda Fluharty <mfluharty@gitlab.com>
Co-authored-by: Dheeraj Joshi <djoshi@gitlab.com>