Prevent deploy token bypass for external authentication

What does this MR do and why?

Prevent deploy token bypass for external authentication (Part 2)

Fix deploy token bypass when by disabling access to the container registry and dependency proxy when external authorization is enabled. Resolves https://gitlab.com/gitlab-org/gitlab/-/issues/382159+

Original MR https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/2950

How to set up and validate locally

1. Save follwing file as external_auth.rb

# frozen_string_literal: true

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'
  gem 'puma'
  gem 'sinatra'
end

require 'sinatra'

post '/' do
  status 403
  'Hello'
end

Sinatra::Application.run!

1. Run that file

ruby external_auth.rb

1. Goto Admin -> Settings -> External authorisation

2. Enter localhost:4567 as the Endpoint and test as the classification label

3. Ensure that dependency proxy and container registry are not accessinle

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.