Some minor change and spec for Account (#3813)

* Introduce domains method to Account relation

Account had followers_domains method, which was excessively specific.
Let relation of Account have domains method instead.

* Move follow_mapping in Account to AccountInteractions

* Introduce shared examples for AccountAvatar inclusion

* Cover Account more

app/models/account.rb

@@ -124,10 +124,6 @@ class Account < ApplicationRecord
     subscription_expires_at.present?
   end
 
-  def followers_domains
-    followers.reorder(nil).pluck('distinct accounts.domain')
-  end
-
   def keypair
     OpenSSL::PKey::RSA.new(private_key || public_key)
   end
@@ -163,6 +159,10 @@ class Account < ApplicationRecord
   end
 
   class << self
+    def domains
+      reorder(nil).pluck('distinct accounts.domain')
+    end
+
     def triadic_closures(account, limit: 5, offset: 0)
       sql = <<-SQL.squish
         WITH first_degree AS (
@@ -236,10 +236,6 @@ class Account < ApplicationRecord
 
       [textsearch, query]
     end
-
-    def follow_mapping(query, field)
-      query.pluck(field).each_with_object({}) { |id, mapping| mapping[id] = true }
-    end
   end
 
   before_create :generate_keys

app/models/concerns/account_interactions.rb

@@ -29,6 +29,12 @@ module AccountInteractions
       blocked_domains = AccountDomainBlock.where(account_id: account_id, domain: accounts_map.values).pluck(:domain)
       accounts_map.map { |id, domain| [id, blocked_domains.include?(domain)] }.to_h
     end
+
+    private
+
+    def follow_mapping(query, field)
+      query.pluck(field).each_with_object({}) { |id, mapping| mapping[id] = true }
+    end
   end
 
   included do

app/workers/pubsubhubbub/distribution_worker.rb

@@ -33,7 +33,7 @@ class Pubsubhubbub::DistributionWorker
     return if stream_entries.empty?
 
     @payload = AtomSerializer.render(AtomSerializer.new.feed(@account, stream_entries))
-    @domains = @account.followers_domains
+    @domains = @account.followers.domains
 
     Pubsubhubbub::DeliveryWorker.push_bulk(@subscriptions.reject { |s| !allowed_to_receive?(s.callback_url) }) do |subscription|
       [subscription.id, @payload]