Refactoring the code for pub sub (#155)

- We were using the attribute name 'channel' to store pubsub tokens, which was confusing.
- switched to faker from ffaker
- spec for contact.rb

spec/models/user_spec.rb

@@ -21,4 +21,20 @@ RSpec.describe User do
     it { is_expected.to have_many(:assigned_inboxes).through(:inbox_members) }
     it { is_expected.to have_many(:messages) }
   end
+
+  describe 'pubsub_token' do
+    let(:user) { create(:user) }
+
+    it 'gets created on object create' do
+      obj = user
+      expect(obj.pubsub_token).not_to eq(nil)
+    end
+
+    it 'does not get updated on object update' do
+      obj = user
+      old_token = obj.pubsub_token
+      obj.update(name: 'test')
+      expect(obj.pubsub_token).to eq(old_token)
+    end
+  end
 end