Merge branch '519958-pipeline-inputs-endpoints-3' into 'master'

Add `inputs` to `POST /projects/:id/trigger/pipeline`

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/183253



Merged-by: Furkan Ayhan <furkanayhn@gmail.com>
Approved-by: Fabio Pitino <fpitino@gitlab.com>
Reviewed-by: Furkan Ayhan <furkanayhn@gmail.com>
Reviewed-by: Fabio Pitino <fpitino@gitlab.com>
Reviewed-by: Marcel Amirault <mamirault@gitlab.com>