Add /api/v1/accounts/familiar_followers to REST API (#17700)

* Add `/api/v1/accounts/familiar_followers` to REST API

* Change hide network preference to be stored consistently for local and remote accounts

* Add dummy classes to migration

* Apply suggestions from code review

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/serializers/rest/familiar_followers_serializer.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class REST::FamiliarFollowersSerializer < ActiveModel::Serializer
+  attribute :id
+
+  has_many :accounts, serializer: REST::AccountSerializer
+
+  def id
+    object.id.to_s
+  end
+end