Create Workshop service for webhooks

[apburnes]

When a user's site kicks off a new build from a Workshop project, it should be able to clone and build the site in the same process as a site's source code from GitHub.

Notes

• Excerpt and link to any relevant slack discussions

Acceptance Criteria

• Update the expected build job params to pull from Github or Workshop Gitlab
• Make sure the git clone can handle private Workshop projects like it does for GitHub now.