Replace RxJava3 code with coroutines (#4290)

This pull request removes the remaining RxJava code and replaces it with
coroutine-equivalent implementations.

- Remove all duplicate methods in `MastodonApi`:
- Methods returning a RxJava `Single` have been replaced by suspending
methods returning a `NetworkResult` in order to be consistent with the
new code.
- _sync_/_async_ method variants are replaced with the _async_ version
only (suspending method), and `runBlocking{}` is used to make the async
variant synchronous.
- Create a custom coroutine-based implementation of `Single` for usage
in Java code where launching a coroutine is not possible. This class can
be deleted after remaining Java code has been converted to Kotlin.
- `NotificationsFragment.java` can subscribe to `EventHub` events by
calling the new lifecycle-aware `EventHub.subscribe()` method. This
allows using the `SharedFlow` as single source of truth for all events.
- Rx Autodispose is replaced by `lifecycleScope.launch()` which will
automatically cancel the coroutine when the Fragment view/Activity is
destroyed.
- Background work is launched in the existing injectable
`externalScope`, since using `GlobalScope` is discouraged.
`externalScope` has been changed to be a `@Singleton` and to use the
main dispatcher by default.
- Transform `ShareShortcutHelper` to an injectable utility class so it
can use the application `Context` and `externalScope` as provided
dependencies to launch a background coroutine.
- Implement a custom Glide extension method
`RequestBuilder.submitAsync()` to do the same thing as
`RequestBuilder.submit().get()` in a non-blocking way. This way there is
no need to switch to a background dispatcher and block a background
thread, and cancellation is supported out-of-the-box.
- An utility method `Fragment.updateRelativeTimePeriodically()` has been
added to remove duplicate logic in `TimelineFragment` and
`NotificationsFragment`, and the logic is now implemented using a simple
coroutine instead of `Observable.interval()`. Note that the periodic
update now happens between onStart and onStop instead of between
onResume and onPause, since the Fragment is not interactive but is still
visible in the started state.
- Rewrite `BottomSheetActivityTest` using coroutines tests.
- Remove all RxJava library dependencies.

app/src/main/java/com/keylesspalace/tusky/receiver/NotificationBlockStateBroadcastReceiver.kt

@@ -24,11 +24,12 @@ import com.keylesspalace.tusky.components.notifications.canEnablePushNotificatio
 import com.keylesspalace.tusky.components.notifications.isUnifiedPushNotificationEnabledForAccount
 import com.keylesspalace.tusky.components.notifications.updateUnifiedPushSubscription
 import com.keylesspalace.tusky.db.AccountManager
+import com.keylesspalace.tusky.di.ApplicationScope
 import com.keylesspalace.tusky.network.MastodonApi
 import dagger.android.AndroidInjection
 import javax.inject.Inject
+import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.DelicateCoroutinesApi
-import kotlinx.coroutines.GlobalScope
 import kotlinx.coroutines.launch
 
 @DelicateCoroutinesApi
@@ -39,6 +40,10 @@ class NotificationBlockStateBroadcastReceiver : BroadcastReceiver() {
     @Inject
     lateinit var accountManager: AccountManager
 
+    @Inject
+    @ApplicationScope
+    lateinit var externalScope: CoroutineScope
+
     override fun onReceive(context: Context, intent: Intent) {
         AndroidInjection.inject(this, context)
         if (Build.VERSION.SDK_INT < 28) return
@@ -60,7 +65,7 @@ class NotificationBlockStateBroadcastReceiver : BroadcastReceiver() {
         accountManager.getAccountByIdentifier(gid)?.let { account ->
             if (isUnifiedPushNotificationEnabledForAccount(account)) {
                 // Update UnifiedPush notification subscription
-                GlobalScope.launch {
+                externalScope.launch {
                     updateUnifiedPushSubscription(
                         context,
                         mastodonApi,

app/src/main/java/com/keylesspalace/tusky/receiver/UnifiedPushBroadcastReceiver.kt

@@ -23,12 +23,13 @@ import androidx.work.WorkManager
 import com.keylesspalace.tusky.components.notifications.registerUnifiedPushEndpoint
 import com.keylesspalace.tusky.components.notifications.unregisterUnifiedPushEndpoint
 import com.keylesspalace.tusky.db.AccountManager
+import com.keylesspalace.tusky.di.ApplicationScope
 import com.keylesspalace.tusky.network.MastodonApi
 import com.keylesspalace.tusky.worker.NotificationWorker
 import dagger.android.AndroidInjection
 import javax.inject.Inject
+import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.DelicateCoroutinesApi
-import kotlinx.coroutines.GlobalScope
 import kotlinx.coroutines.launch
 import org.unifiedpush.android.connector.MessagingReceiver
 
@@ -44,6 +45,10 @@ class UnifiedPushBroadcastReceiver : MessagingReceiver() {
     @Inject
     lateinit var mastodonApi: MastodonApi
 
+    @Inject
+    @ApplicationScope
+    lateinit var externalScope: CoroutineScope
+
     override fun onReceive(context: Context, intent: Intent) {
         super.onReceive(context, intent)
         AndroidInjection.inject(this, context)
@@ -61,9 +66,7 @@ class UnifiedPushBroadcastReceiver : MessagingReceiver() {
         AndroidInjection.inject(this, context)
         Log.d(TAG, "Endpoint available for account $instance: $endpoint")
         accountManager.getAccountById(instance.toLong())?.let {
-            // Launch the coroutine in global scope -- it is short and we don't want to lose the registration event
-            // and there is no saner way to use structured concurrency in a receiver
-            GlobalScope.launch {
+            externalScope.launch {
                 registerUnifiedPushEndpoint(context, mastodonApi, accountManager, it, endpoint)
             }
         }
@@ -76,7 +79,7 @@ class UnifiedPushBroadcastReceiver : MessagingReceiver() {
         Log.d(TAG, "Endpoint unregistered for account $instance")
         accountManager.getAccountById(instance.toLong())?.let {
             // It's fine if the account does not exist anymore -- that means it has been logged out
-            GlobalScope.launch { unregisterUnifiedPushEndpoint(mastodonApi, accountManager, it) }
+            externalScope.launch { unregisterUnifiedPushEndpoint(mastodonApi, accountManager, it) }
         }
     }
 }