Throwing errors in ClassroomListActivity because of model

[Zaid-0504]

In this there is no model directory available inside org.oppia.android.app i am an able to find the all the required file imported from the model directory.

[adhiamboperes]

Hi @Zaid-0504, you encountered this because you used a version of android studio that is not compatible with our gradle version. However, we have moved away from Gradle and are now working with Bazel. Please follow https://github.com/oppia/oppia-android/wiki/Oppia-Bazel-Setup-Instructions. to setup Bazel, and refer to #5643 to set up the Bazel plugin in order to be able to continue building on your current version of AS.