THREESCALE-15279: Expose audience_mapper_client_id in application API

app/models/cinstance.rb

@@ -5,7 +5,7 @@ class Cinstance < Contract
 
   self.background_deletion = %i[referrer_filters application_keys alerts]
 
-  delegate :backend_version, to: :service, allow_nil: true
+  delegate :backend_version, :audience_mapper_client_id, to: :service, allow_nil: true
 
   belongs_to :plan, class_name: 'ApplicationPlan', foreign_key: :plan_id, inverse_of: :cinstances
   alias application_plan plan

app/models/proxy.rb

@@ -146,6 +146,16 @@ def find_policy_config_by(name:, version:)
     policies_config.find_by(name: name, version: version)
   end
 
+  def audience_mapper_client_id
+    policy = find_policy_config_by(name: 'token_introspection', version: 'builtin')
+    return unless policy&.enabled
+
+    config = policy.configuration&.with_indifferent_access || {}
+    return unless config[:auth_type] == 'use_3scale_oidc_issuer_endpoint' || config[:auth_type].blank?
+
+    URI.parse(oidc_issuer_endpoint).user rescue nil
+  end
+
   def oidc_configuration
     super || build_oidc_configuration(standard_flow_enabled: true)
   end

app/models/service.rb

@@ -589,7 +589,7 @@ def notify_deletion
   delegate :oauth?, to: :authentication_scheme?
 
   delegate :authentication_method, to: :proxy, prefix: true, allow_nil: true
-  delegate :oidc?, :pending_affecting_changes?, to: :proxy, allow_nil: true
+  delegate :oidc?, :pending_affecting_changes?, :audience_mapper_client_id, to: :proxy, allow_nil: true
 
   def authentication_scheme?
     backend_version.to_s.inquiry

app/representers/cinstance_representer.rb

@@ -40,6 +40,7 @@ module CinstanceRepresenter
 
   with_options(if: ->(*) { service.oidc? }, render_nil: true) do |oidc|
     oidc.property :oidc_configuration, decorator: OIDCConfigurationRepresenter, wrap: false
+    oidc.property :audience_mapper_client_id
   end
 
   def provider_verification_key

test/unit/proxy_test.rb

@@ -843,6 +843,67 @@ class ProxyConfigAffectingChangesTest < ActiveSupport::TestCase
     end
   end
 
+  class AudienceMapperClientIdTest < ActiveSupport::TestCase
+    ISSUER_URL = 'https://introspection-client:s3cr3t@sso.example.com/auth/realms/master'
+    TOKEN_INTROSPECTION_POLICY = { name: 'token_introspection', version: 'builtin' }.freeze
+
+    def proxy_with_policy(config)
+      proxy = FactoryBot.build(:simple_proxy)
+      proxy.policies_config = [TOKEN_INTROSPECTION_POLICY.merge(configuration: config, enabled: true)]
+      proxy
+    end
+
+    test 'returns user from oidc_issuer_endpoint when auth_type is use_3scale_oidc_issuer_endpoint' do
+      proxy = proxy_with_policy('auth_type' => 'use_3scale_oidc_issuer_endpoint')
+      proxy.oidc_issuer_endpoint = ISSUER_URL
+      assert_equal 'introspection-client', proxy.audience_mapper_client_id
+    end
+
+    test 'returns user from oidc_issuer_endpoint when auth_type is blank' do
+      proxy = proxy_with_policy({})
+      proxy.oidc_issuer_endpoint = ISSUER_URL
+      assert_equal 'introspection-client', proxy.audience_mapper_client_id
+    end
+
+    test 'returns nil when auth_type is client_id+client_secret' do
+      proxy = proxy_with_policy('auth_type' => 'client_id+client_secret', 'client_id' => 'my-introspection-client')
+      assert_nil proxy.audience_mapper_client_id
+    end
+
+    test 'returns nil when auth_type is client_secret_jwt' do
+      proxy = proxy_with_policy('auth_type' => 'client_secret_jwt', 'client_id' => 'my-introspection-client')
+      assert_nil proxy.audience_mapper_client_id
+    end
+
+    test 'returns nil when auth_type is private_key_jwt' do
+      proxy = proxy_with_policy('auth_type' => 'private_key_jwt', 'client_id' => 'my-introspection-client')
+      assert_nil proxy.audience_mapper_client_id
+    end
+
+    test 'returns nil when policy is disabled' do
+      proxy = FactoryBot.build(:simple_proxy)
+      proxy.policies_config = [TOKEN_INTROSPECTION_POLICY.merge(configuration: { 'auth_type' => 'use_3scale_oidc_issuer_endpoint' }, enabled: false)]
+      assert_nil proxy.audience_mapper_client_id
+    end
+
+    test 'returns nil when token introspection policy is absent' do
+      proxy = FactoryBot.build(:simple_proxy)
+      assert_nil proxy.audience_mapper_client_id
+    end
+
+    test 'returns nil when oidc_issuer_endpoint has no user' do
+      proxy = proxy_with_policy('auth_type' => 'use_3scale_oidc_issuer_endpoint')
+      proxy.oidc_issuer_endpoint = 'https://sso.example.com/auth/realms/master'
+      assert_nil proxy.audience_mapper_client_id
+    end
+
+    test 'returns nil when oidc_issuer_endpoint is blank' do
+      proxy = proxy_with_policy('auth_type' => 'use_3scale_oidc_issuer_endpoint')
+      proxy.oidc_issuer_endpoint = nil
+      assert_nil proxy.audience_mapper_client_id
+    end
+  end
+
   class StaleObjectErrorTest < ActiveSupport::TestCase
     test 'proxy does not raise stale object error on concurrent touch' do
       class ProxyWithFiber < ::Proxy