Change the app_usages API to accept array of data

- Add foreignkey to device for AppUsage
- Rename the route to app_usage from app_usage/create

spec/controllers/app_usages_controller_spec.rb

@@ -9,12 +9,12 @@ RSpec.describe AppUsagesController, type: :controller do
         request.env['HTTP_AUTHORIZATION'] = ActionController::HttpAuthentication::Token.encode_credentials(device.access_token)
       end
       it "Valid params" do
-        post :create, app_usage: attributes_for(:app_usage), format: :json
+        post :create, app_usage: [attributes_for(:app_usage)], format: :json
         expect(response).to have_http_status(:success)
       end
 
       it "InValid Params" do
-        post :create, app_usage: attributes_for(:invalid_app_usage), format: :json
+        post :create, app_usage: [attributes_for(:invalid_app_usage)], format: :json
         expect(response).to have_http_status(:unprocessable_entity)
       end
     end

spec/models/app_usage_spec.rb

@@ -6,4 +6,5 @@ RSpec.describe AppUsage, type: :model do
   it { should validate_presence_of :package_name } 
   it { should validate_presence_of :usage_duration_in_seconds } 
   it { should validate_presence_of :used_on } 
+  it { should belong_to :device }
 end