Add network settings graphql endpoints

What does this MR do and why?

Followup to !229563 (merged) - which added the setting data to the database.

This MR adds graphql endpoints for instance-level and TLG allowed/denied domain list settings. These settings are arrays of allowed / denied domains and will be editable via a paginated editor in the front-end in a followup MR. The MR only provides the read functionality, and a followup with have the mutations for saving changes.

References

Relates to https://gitlab.com/gitlab-org/gitlab/-/work_items/593149

How to set up and validate locally

Add some data for your instance:

::Ai::Setting.instance.update!(allowed_domains: (1..30).map { |x| "instance_domain#{x}.com" })

Add some data for a namespace:

namespace = ::Namespace.find_by_path "gitlab-duo"
namespace.update(ai_allowed_domains: (1..30).map { |x| "namespace_domain_#{x}.com" })

Query your instance:

query domainSettings {
  aiDomainSettings(domainSettingType: ALLOWED, first:10, after:null, search:"") {
    nodes
    pageInfo { hasNextPage endCursor }
  }
}

Query a namespace:

query domainSettingsForNamespace {
  namespace(fullPath: "gitlab-duo") {
    id,
    name,
    aiDomainSettings(domainSettingType: ALLOWED, first:20, after:null, search:"") {
      nodes
      pageInfo { hasNextPage endCursor }
    }
  }
}

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.