UX: Display group tabs in user's messages tab for non-staff as well.

https://meta.discourse.org/t/group-inboxes-in-user-messages/86787

app/serializers/basic_group_serializer.rb

@@ -43,7 +43,7 @@ class BasicGroupSerializer < ApplicationSerializer
   end
 
   def include_has_messages?
-    staff?
+    staff? || scope.can_see_group_messages?(object)
   end
 
   def include_bio_raw?

spec/serializers/basic_group_serializer_spec.rb

@@ -3,7 +3,7 @@ require 'rails_helper'
 describe BasicGroupSerializer do
   let(:guardian) { Guardian.new }
   let(:group) { Fabricate(:group) }
-  subject { described_class.new(group, scope: Guardian.new, root: false) }
+  subject { described_class.new(group, scope: guardian, root: false) }
 
   describe '#display_name' do
     describe 'automatic group' do
@@ -26,17 +26,52 @@ describe BasicGroupSerializer do
   describe '#bio_raw' do
     let(:group) { Fabricate(:group, bio_raw: 'testing') }
 
-    let(:user) do
-      user = Fabricate(:user)
-      group.add_owner(user)
-      user
+    subject do
+      described_class.new(group, scope: guardian, root: false, owner_group_ids: [group.id])
     end
 
-    let(:guardian) { Guardian.new(user) }
-
     describe 'group owner' do
+      let(:user) do
+        user = Fabricate(:user)
+        group.add_owner(user)
+        user
+      end
+
       it 'should include bio_raw' do
-        expect(subject.bio_raw).to eq('testing')
+        expect(subject.as_json[:bio_raw]).to eq('testing')
+      end
+    end
+  end
+
+  describe '#has_messages' do
+    let(:group) { Fabricate(:group, has_messages: true) }
+
+    describe 'for a staff user' do
+      let(:guardian) { Guardian.new(Fabricate(:moderator)) }
+
+      it 'should be present' do
+        expect(subject.as_json[:has_messages]).to eq(true)
+      end
+    end
+
+    describe 'for a group user' do
+      let(:user) { Fabricate(:user) }
+      let(:guardian) { Guardian.new(user) }
+
+      before do
+        group.add(user)
+      end
+
+      it 'should be present' do
+        expect(subject.as_json[:has_messages]).to eq(true)
+      end
+    end
+
+    describe 'for a normal user' do
+      let(:guardian) { Guardian.new(Fabricate(:user)) }
+
+      it 'should not be present' do
+        expect(subject.as_json[:has_messages]).to eq(nil)
       end
     end
   end