chore: Add a check for defined labels in SDK API (#1259)

spec/controllers/api/v1/widget/labels_controller_spec.rb

@@ -12,8 +12,24 @@ RSpec.describe '/api/v1/widget/labels', type: :request do
   describe 'POST /api/v1/widget/labels' do
     let(:params) { { website_token: web_widget.website_token, label: 'customer-support' } }
 
-    context 'with correct website token' do
-      it 'returns the list of labels' do
+    context 'with correct website token and undefined label' do
+      it 'does not add the label' do
+        post '/api/v1/widget/labels',
+             params: params,
+             headers: { 'X-Auth-Token' => token },
+             as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(conversation.reload.label_list.count).to eq 0
+      end
+    end
+
+    context 'with correct website token and a defined label' do
+      before do
+        account.labels.create(title: 'customer-support')
+      end
+
+      it 'add the label to the conversation' do
         post '/api/v1/widget/labels',
              params: params,
              headers: { 'X-Auth-Token' => token },