Make AccountPreferenceDataStore injectable (#3653)

This will make tests that need it easier.

- Rename from AccountPreferenceHandler
- Inject its dependencies
- Create an injectable CoroutineScope it can use for launching coroutines
- Use it in AccountPreferences

app/src/main/java/com/keylesspalace/tusky/di/AppComponent.kt

@@ -29,6 +29,7 @@ import javax.inject.Singleton
 @Component(
     modules = [
         AppModule::class,
+        CoroutineScopeModule::class,
         NetworkModule::class,
         AndroidSupportInjectionModule::class,
         ActivitiesModule::class,

app/src/main/java/com/keylesspalace/tusky/di/CoroutineScopeModule.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2023 Tusky Contributors
+ *
+ * This file is a part of Tusky.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Tusky; if not,
+ * see <http://www.gnu.org/licenses>.
+ */
+
+package com.keylesspalace.tusky.di
+
+import dagger.Module
+import dagger.Provides
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import javax.inject.Qualifier
+
+/**
+ * Scope for potentially long-running tasks that should outlive the viewmodel that
+ * started them. For example, if the API call to bookmark a status is taking a long
+ * time, that call should not be cancelled because the user has navigated away from
+ * the viewmodel that made the call.
+ *
+ * @see https://developer.android.com/topic/architecture/data-layer#make_an_operation_live_longer_than_the_screen
+ */
+@Retention(AnnotationRetention.BINARY)
+@Qualifier
+annotation class ApplicationScope
+
+@Module
+class CoroutineScopeModule {
+    @ApplicationScope
+    @Provides
+    fun providesApplicationScope() = CoroutineScope(SupervisorJob() + Dispatchers.Default)
+}