Remove domain validation from DAST

The domain validation in DAST is an opt-in in order to opt-out and therefore does not have very good use cases. The validation also conflicts with the approach of on-demand DAST scanning and introduces confusion.

In 14.0 we will remove this functionality.

Proposal

• Remove the functionality
• Update documentation to eliminate the use, https://docs.gitlab.com/ee/user/application_security/dast/#domain-validation
• Issue deprecation notice.

Technical Details

Use config.dast_major_version to ensure that the check and related argument definitions are not present when the DAST version >= 2.0