Fix part of #5344: Introduce & modify controllers to support multiple classrooms

domain/src/main/java/org/oppia/android/domain/profile/ProfileManagementController.kt

@@ -71,6 +71,10 @@ private const val SET_SURVEY_LAST_SHOWN_TIMESTAMP_PROVIDER_ID =
   "record_survey_last_shown_timestamp_provider_id"
 private const val RETRIEVE_SURVEY_LAST_SHOWN_TIMESTAMP_PROVIDER_ID =
   "retrieve_survey_last_shown_timestamp_provider_id"
+private const val SET_LAST_SELECTED_CLASSROOM_ID_PROVIDER_ID =
+  "set_last_selected_classroom_id_provider_id"
+private const val RETRIEVE_LAST_SELECTED_CLASSROOM_ID_PROVIDER_ID =
+  "retrieve_last_selected_classroom_id_provider_id"
 
 /** Controller for retrieving, adding, updating, and deleting profiles. */
 @Singleton
@@ -851,6 +855,47 @@ class ProfileManagementController @Inject constructor(
     }
   }
 
+  /**
+   * Sets the last selected [classroomId] for the specified [profileId]. Returns a [DataProvider]
+   * indicating whether the save was a success.
+   */
+  fun updateLastSelectedClassroomId(
+    profileId: ProfileId,
+    classroomId: String
+  ): DataProvider<Any?> {
+    val deferred = profileDataStore.storeDataWithCustomChannelAsync(
+      updateInMemoryCache = true
+    ) { profileDatabase ->
+      val profile = profileDatabase.profilesMap[profileId.internalId]
+      val updatedProfile = profile?.toBuilder()?.setLastSelectedClassroomId(
+        classroomId
+      )?.build()
+      val profileDatabaseBuilder = profileDatabase.toBuilder().putProfiles(
+        profileId.internalId,
+        updatedProfile
+      )
+      Pair(profileDatabaseBuilder.build(), ProfileActionStatus.SUCCESS)
+    }
+    return dataProviders.createInMemoryDataProviderAsync(
+      SET_LAST_SELECTED_CLASSROOM_ID_PROVIDER_ID
+    ) {
+      return@createInMemoryDataProviderAsync getDeferredResult(profileId, null, deferred)
+    }
+  }
+
+  /**
+   * Returns a [DataProvider] containing a nullable last selected classroom ID for the specified
+   * [profileId].
+   */
+  fun retrieveLastSelectedClassroomId(
+    profileId: ProfileId
+  ): DataProvider<String?> {
+    return profileDataStore.transformAsync(RETRIEVE_LAST_SELECTED_CLASSROOM_ID_PROVIDER_ID) {
+      val lastSelectedClassroomId = it.profilesMap[profileId.internalId]?.lastSelectedClassroomId
+      AsyncResult.Success(lastSelectedClassroomId)
+    }
+  }
+
   private suspend fun getDeferredResult(
     profileId: ProfileId?,
     name: String?,

domain/src/main/java/org/oppia/android/domain/topic/TopicListController.kt

@@ -29,6 +29,7 @@ import org.oppia.android.app.model.TopicProgress
 import org.oppia.android.app.model.TopicRecord
 import org.oppia.android.app.model.TopicSummary
 import org.oppia.android.app.model.UpcomingTopic
+import org.oppia.android.domain.classroom.TEST_CLASSROOM_ID_0
 import org.oppia.android.domain.translation.TranslationController
 import org.oppia.android.domain.util.JsonAssetRetriever
 import org.oppia.android.domain.util.getStringFromObject
@@ -60,11 +61,6 @@ const val SUBTOPIC_TOPIC_ID = 1
 const val SUBTOPIC_TOPIC_ID_2 = 2
 const val RATIOS_TOPIC_ID = "omzF4oqgeTXd"
 
-// TODO(#5344): Move these classroom ids to [ClassroomController].
-const val TEST_CLASSROOM_ID_0 = "test_classroom_id_0"
-const val TEST_CLASSROOM_ID_1 = "test_classroom_id_1"
-const val TEST_CLASSROOM_ID_2 = "test_classroom_id_2"
-
 val TOPIC_THUMBNAILS = mapOf(
   FRACTIONS_TOPIC_ID to createTopicThumbnail0(),
   RATIOS_TOPIC_ID to createTopicThumbnail1(),