Update policies to support Self-hosted DAP SKU alongside Duo Enterprise

What does this MR do and why?

Update policies and GQL logic to satisfy the following new rules:

• Duo Enterprise customers: Continue existing self-hosting for Duo Enterprise features (Code Suggestions, etc.) + cloud-connected DAP only
• Self-hosted DAP SKU customers: self-hosted models for DAP feature settings. All classic feature settings remain as is.

References

https://gitlab.com/gitlab-org/gitlab/-/work_items/582207+

Screenshots or screen recordings

	Offline license	Online license
Duo Enterprise add-on (no SKU)	duo_enterprise_offline.mov Cannot update DAP feature setting to self-hosted model programatically:	duo_enterprise_online.mov Cannot update DAP feature setting to self-hosted model programatically:
With SKU	sku_offline.mov	❌ SKU is available with offline license only

How to set up and validate locally

Setup for no SKU (Duo Enterprise add-on)

• Run the following setup script to get Duo Enterprise add on: GITLAB_SIMULATE_SAAS=0 bundle exec 'rake gitlab:duo:setup'
• Update offline_cloud_license? in ee/app/models/license.rb to return false if testing for offline license behavior.

Setup for SKU

• Enable self_hosted_dap_sku flag.
• Update offline_cloud_license? in ee/app/models/license.rb to return false

Steps:

• Run GDK on non-SASS mode: GITLAB_SIMULATE_SAAS=0 gdk start

• Go to /admin/gitlab_duo/self_hosted

• Observe the following behaviors

  	Self-hosted models View and set to self-hosted model Create/edit/delete self-hosted model	GitLab-managed models View and set to GitLab-managed model
  DAP SKU with offline license	Classic: DAP:	Classic: ❌ DAP: ❌
  Duo Enterprise with offline license	Classic: DAP: ❌	Classic: ❌ DAP: ❌
  Duo Enterprise with online license	Classic: DAP: ❌	Classic: DAP:

• To test out setting self-hosted model programatically, use the GQL explorer (/-/graphql-explorer ):

  mutation updateAiFeatureSetting($input: AiFeatureSettingUpdateInput!) {
    aiFeatureSettingUpdate(input: $input) {
      errors
      __typename
    }
  }
  
  # variables
  {
    "input": {
      "features": [
        "DUO_AGENT_PLATFORM"
      ],
      "provider": "SELF_HOSTED",
      "aiSelfHostedModelId": "gid://gitlab/Ai::SelfHostedModel/11",
      "offeredModelRef": null
    }
  }

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