Check namespace setting for XRay scan

What does this MR do and why?

Check namespace setting for XRay scan

AI AddOn feature is not available yet. Add feature flag check to XRay scan endpoint to respect that. Since AI AddOn is not available, lets reuse code suggestion flow for authorisation access.

Make sure that namespace has code suggestions enabled before running scan.

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Before	After

How to set up and validate locally

1. Make sure that AI Gateway is working on your local env
2. Select Ci::Build from namespace with code suggestions add on purchased
3. Update build state to running
4. Set build token to any value eg: secret

project = Project.find 2
build = project.builds.first
build.set_token 'secret'
build.status = "running"
build.save
namespace = build.project.namespace

1. Run gdk as SaaS https://docs.gitlab.com/ee/development/ee_features.html#simulate-a-saas-instance
2. Disable ::Feature.disable(:purchase_code_suggestions)

Use build id and token to make curl request to API endpoint

 curl -v -X POST -H "Content-Type: Application/json"  http://gdk.test:3000/api/v4/internal/jobs/1/x_ray/scan --data '{
  "token": "tajnyToken",
  "prompt_components": [
     {
       "type":"x_ray_package_file_prompt",
       "payload":{
         "prompt": "Human: Parse following content of {file_name}. Respond using only valid JSON with list of libraries available to use and their short description\n\n{file_name} content:\n\n```\n{content}\n```\n\n Assistant: {{\n\"libraries\":[{{\"name\": \"",
         "provider": "anthropic",
         "model": "claude-2.0"
       },
       "metadata": { "scannerVersion": "0.0.1" }
     }
  ]
 }'

To get authorised with ::Feature.enable(:purchase_code_suggestions) enabled

FactoryBot.create(:gitlab_subscription_add_on_purchase, add_on: FactoryBot.create(:gitlab_subscription_add_on), namespace: namespace)

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