Feature: API to get most used labels (#447)

* Add most-used labels API

* Filter conversation by labels

* Move match_all to any query

Co-authored-by: Pranav Raj S <pranavrajs@gmail.com>

spec/controllers/api/v1/labels_controller_spec.rb

@@ -31,4 +31,29 @@ RSpec.describe 'Label API', type: :request do
       end
     end
   end
+
+  describe 'GET /api/v1/labels/most_used' do
+    context 'when it is an unauthenticated user' do
+      it 'returns unauthorized' do
+        get '/api/v1/labels'
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when it is an authenticated user' do
+      let(:agent) { create(:user, account: account, role: :agent) }
+
+      it 'returns most used labels' do
+        get '/api/v1/labels/most_used',
+            headers: agent.create_new_auth_token,
+            params: { count: 1 },
+            as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(response.body).to include('label1')
+        expect(response.body).not_to include('label2')
+      end
+    end
+  end
 end