Add notifications of severed relationships (#27511)

app/models/relationship_severance_event.rb

@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: relationship_severance_events
+#
+#  id          :bigint(8)        not null, primary key
+#  type        :integer          not null
+#  target_name :string           not null
+#  purged      :boolean          default(FALSE), not null
+#  created_at  :datetime         not null
+#  updated_at  :datetime         not null
+#
+class RelationshipSeveranceEvent < ApplicationRecord
+  self.inheritance_column = nil
+
+  has_many :severed_relationships, inverse_of: :relationship_severance_event, dependent: :delete_all
+
+  enum type: {
+    domain_block: 0,
+    user_domain_block: 1,
+    account_suspension: 2,
+  }
+
+  scope :about_local_account, ->(account) { where(id: SeveredRelationship.about_local_account(account).select(:relationship_severance_event_id)) }
+
+  def import_from_active_follows!(follows)
+    import_from_follows!(follows, true)
+  end
+
+  def import_from_passive_follows!(follows)
+    import_from_follows!(follows, false)
+  end
+
+  def affected_local_accounts
+    Account.where(id: severed_relationships.select(:local_account_id))
+  end
+
+  private
+
+  def import_from_follows!(follows, active)
+    SeveredRelationship.insert_all(
+      follows.pluck(:account_id, :target_account_id, :show_reblogs, :notify, :languages).map do |account_id, target_account_id, show_reblogs, notify, languages|
+        {
+          local_account_id: active ? account_id : target_account_id,
+          remote_account_id: active ? target_account_id : account_id,
+          show_reblogs: show_reblogs,
+          notify: notify,
+          languages: languages,
+          relationship_severance_event_id: id,
+          direction: active ? :active : :passive,
+        }
+      end
+    )
+  end
+end