Add ActivityPub representation for identity proofs (#10414)

* Add ActivityPub representation for identity proofs

* Add tests

app/serializers/activitypub/actor_serializer.rb

@@ -6,7 +6,7 @@ class ActivityPub::ActorSerializer < ActivityPub::Serializer
   context :security
 
   context_extensions :manually_approves_followers, :featured, :also_known_as,
-                     :moved_to, :property_value, :hashtag, :emoji
+                     :moved_to, :property_value, :hashtag, :emoji, :identity_proof
 
   attributes :id, :type, :following, :followers,
              :inbox, :outbox, :featured,
@@ -115,7 +115,7 @@ class ActivityPub::ActorSerializer < ActivityPub::Serializer
   end
 
   def virtual_attachments
-    object.fields
+    object.fields + object.identity_proofs.active
   end
 
   def moved_to
@@ -158,4 +158,24 @@ class ActivityPub::ActorSerializer < ActivityPub::Serializer
       Formatter.instance.format_field(object.account, object.value)
     end
   end
+
+  class AccountIdentityProofSerializer < ActivityPub::Serializer
+    attributes :type, :name, :signature_algorithm, :signature_value
+
+    def type
+      'IdentityProof'
+    end
+
+    def name
+      object.provider_username
+    end
+
+    def signature_algorithm
+      object.provider
+    end
+
+    def signature_value
+      object.token
+    end
+  end
 end