Add documentation to dependency injection components and modules.

presentation/src/main/java/com/fernandocejas/android10/sample/presentation/internal/di/HasComponent.java

@@ -4,6 +4,9 @@
  */
 package com.fernandocejas.android10.sample.presentation.internal.di;
 
+/**
+ * Interface representing a contract for clients that contains a component for dependency injection.
+ */
 public interface HasComponent<C> {
   C getComponent();
 }

presentation/src/main/java/com/fernandocejas/android10/sample/presentation/internal/di/components/UserComponent.java

@@ -11,6 +11,10 @@ import com.fernandocejas.android10.sample.presentation.view.fragment.UserDetails
 import com.fernandocejas.android10.sample.presentation.view.fragment.UserListFragment;
 import dagger.Component;
 
+/**
+ * A scope {@link com.fernandocejas.android10.sample.presentation.internal.di.PerActivity} component.
+ * Injects user specific Fragments.
+ */
 @PerActivity
 @Component(dependencies = ApplicationComponent.class, modules = {ActivityModule.class, UserModule.class})
 public interface UserComponent extends ActivityComponent {

presentation/src/main/java/com/fernandocejas/android10/sample/presentation/internal/di/modules/UserModule.java

@@ -12,6 +12,9 @@ import com.fernandocejas.android10.sample.presentation.internal.di.PerActivity;
 import dagger.Module;
 import dagger.Provides;
 
+/**
+ * Dagger module that provides user related collaborators.
+ */
 @Module
 public class UserModule {
   @Provides @PerActivity GetUserListUseCase provideGetUserListUseCase(GetUserListUseCaseImpl getUserListUseCase) {