Add document to describe ZAP Server Parameters

What does this MR do?

This MR introduces a new internal DAST document, which aims to describe ZAP server parameters.

See thread where this was discussed.

What are the relevant issue numbers?

n/a

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Job definition example
  • Vendored CI Templates (also in CE)
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer