Provide branch information from dastProfiles [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

adds a new field called branch to the dastProfile GraphQL type and a new feature flag to indicate that the field is experimental.

Why?

this will allow users to understand the status of the branch their scan will be run against. for now, this will be the project's default branch but later in %13.10 this will be a user-defined branch.

Example

Enable Flag

echo "Feature.enable(:dast_branch_selection)" | rails c

Query

{
  project(fullPath: "namespace6/project6") {
    dastProfiles {
      nodes {
        id
        branch {
          name
          exists
        }
      }
    }
  }
}

Related Issue(s)

• #322672 (closed) rollout issue
• #322526 (closed)

Does this MR meet the acceptance criteria?

Conformity

• [ ] Changelog entry change behind feature flag
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team