DAST Site profile - Edit functionality for Authentication, Request headers & Excluded Urls - Frontend

• backend counterpart: #225406 (closed)

Summary

This issue should allow users to edit these new fields in an existing DAST Site Profile

1. Authentication fields
2. Excluded Urls
3. Request headers

Implementation Plan

• Add the newly added fields in
  • ee/app/views/projects/security/dast_site_profiles/edit.html.haml with dummy values until backend is ready
  • ee/app/assets/javascripts/security_configuration/dast_site_profiles_form/index.js
  • Push these changes behind the feature flag
• Update specs ee/spec/views/projects/security/dast_site_profiles/edit.html.haml_spec.rb
• Update GraphQL fields in the dastSiteProfileUpdate mutation
• Handle the following edge case discussed at #225406 (comment 455038320)
  • Sensitive fields should be shown empty / asteriked initially
  • frontend should send the sensitive fields only when user makes any attempt to update those values.