Enable MR auto-creation for DAST CI/CD configuration process

Proposal

Currently for DAST, we only auto-generate the YAML code during the CI/CD configuration process and present it to the user to copy into their .gitlab-ci.yml file. Instead of using this mechanism going forward, in order to improve the workflow experience, we need to auto-create the MR to merge the YAML into the .gitlab-ci.yml file. We should leverage the existing MR creation that is used by SAST and Dependency Scanning, but improve the process, since auto-generating the DAST code is more complicated than the other categories. We should take into account the existing stages, parse the YAML correctly, and intelligently merge the DAST stage and configuration into the file.

Requirements

• New button on the configuration page to "Merge changes"
• Code merged intelligently into existing .gitlab-ci.yml file, taking into account existing stages and structure
• New branch created with commit for "Enabling DAST in .gitlab-ci.yml, if it doesn't exist"
• User directed to new MR creation page