Add administrators UserSegment

We need a user segment to have only administrators as recipients of both
newsletters and notifications

config/locales/en/admin.yml

@@ -518,6 +518,7 @@ en:
         title: 'Moderators: User search'
     segment_recipient:
       all_users: All users
+      administrators: Administrators
       proposal_authors: Proposal authors
       investment_authors: Investment authors in the current budget
       feasible_and_undecided_investment_authors: Authors of feasible or undecided investments in the current budget

config/locales/es/admin.yml

@@ -517,6 +517,7 @@ es:
         title: 'Moderadores: Búsqueda de usuarios'
     segment_recipient:
       all_users: Todos los usuarios
+      administrators: Administradores
       proposal_authors: Usuarios autores de propuestas
       investment_authors: Usuarios autores de proyectos de gasto en los actuales presupuestos
       feasible_and_undecided_investment_authors: Usuarios autores de proyectos de gasto viables o sin decidir en los actuales presupuestos

lib/user_segments.rb

@@ -1,5 +1,6 @@
 class UserSegments
   SEGMENTS = %w(all_users
+                administrators
                 proposal_authors
                 investment_authors
                 feasible_and_undecided_investment_authors
@@ -10,6 +11,10 @@ class UserSegments
     User.active
   end
 
+  def self.administrators
+    all_users.administrators
+  end
+
   def self.proposal_authors
     author_ids(Proposal.not_archived.not_retired.pluck(:author_id).uniq)
   end

spec/lib/user_segments_spec.rb

@@ -15,6 +15,18 @@ describe UserSegments do
     end
   end
 
+  describe "#administrators" do
+    it "returns all active administrators users" do
+      active_user = create(:user)
+      active_admin = create(:administrator).user
+      erased_user = create(:user, erased_at: Time.current)
+
+      expect(described_class.administrators).to include active_admin
+      expect(described_class.administrators).not_to include active_user
+      expect(described_class.administrators).not_to include erased_user
+    end
+  end
+
   describe "#proposal_authors" do
     it "returns users that have created a proposal" do
       proposal = create(:proposal, author: user1)