Simplify push notification flow by using locally stored values for pending pushes (#6258)

* Create `PushRequest` in push history DB: this will be used to store requests for push notifications, either pending or completed ones.

* Rename `WorkManagerRequest` to `WorkManagerRequestBuilder`: make its `build` method return a list of `WorkManagerRequestWrapper`, which can be used to enqueue normal or unique workers.

* Rename `PerformDatabaseVacuumRequestBuilder` and adapt it to the new API.

* Adjust other components using `WorkManagerRequest`.

* Replace `SyncNotificationWorkManagerRequestBuilder` with `SyncPendingNotificationsRequestBuilder` and `FetchNotificationsWorker` with `FetchPendingNotificationsWorker`: this new pair of request builder and worker allow enqueuing requests for a session id and, once the worker runs, retrieve all the pending request data and use it to fetch the associated events. This simplifies quite a bit how this data had to be passed or grouped, since it's no longer necessary to do so

* Add new methods to `PushHistoryService` to modify the `PushDatabase`:

- insertOrUpdatePushRequest
- insertOrUpdatePushRequests
- getPendingPushRequests
- removeOldPushRequests

* Make `PushHandler` just handle incoming pushes: those will be inserted into the pending push request table in DB, then handled by the new worker. Once the process finished, a new `NotificationResultProcessor` will handle the results and what needs to be done with them (call ringing, displaying notifications, etc.)

* Add `requestType` optional parameter to `WorkManagerScheduler.cancel` so we can decide to only cancel some kinds of requests.

* Add migration to remove existing work manager requests for fetching notifications, since the previous worker class no longer exists.

libraries/workmanager/api/src/main/kotlin/io/element/android/libraries/workmanager/api/WorkManagerRequest.kt

@@ -1,15 +0,0 @@
-/*
- * Copyright (c) 2025 Element Creations Ltd.
- * Copyright 2025 New Vector Ltd.
- *
- * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
- * Please see LICENSE files in the repository root for full details.
- */
-
-package io.element.android.libraries.workmanager.api
-
-import androidx.work.WorkRequest
-
-interface WorkManagerRequest {
-    fun build(): Result<List<WorkRequest>>
-}

libraries/workmanager/api/src/main/kotlin/io/element/android/libraries/workmanager/api/WorkManagerRequestBuilder.kt

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ * Copyright 2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.workmanager.api
+
+import androidx.work.ExistingWorkPolicy
+import androidx.work.WorkRequest
+
+/**
+ * A base class that can be customized to [build] work requests to schedule in `WorkManager`.
+ */
+interface WorkManagerRequestBuilder {
+    /**
+     * Builds a work request wrapper using the provided data.
+     */
+    suspend fun build(): Result<List<WorkManagerRequestWrapper>>
+}
+
+/**
+ * A wrapper that allows us to avoid using Android APIs directly when scheduling workers.
+ */
+data class WorkManagerRequestWrapper(
+    val request: WorkRequest,
+    val type: WorkManagerWorkerType = WorkManagerWorkerType.Default,
+)
+
+/**
+ * The type of worker to use when scheduling the task.
+ */
+sealed interface WorkManagerWorkerType {
+    /**
+     * This allows a single worker instance with the [name] id to run at the same time. Its [policy] can be customized.
+     */
+    data class Unique(val name: String, val policy: ExistingWorkPolicy) : WorkManagerWorkerType
+
+    /**
+     * The default worker type, with no custom rules.
+     */
+    data object Default : WorkManagerWorkerType
+}

libraries/workmanager/api/src/main/kotlin/io/element/android/libraries/workmanager/api/WorkManagerScheduler.kt

@@ -11,9 +11,21 @@ package io.element.android.libraries.workmanager.api
 import io.element.android.libraries.matrix.api.core.SessionId
 
 interface WorkManagerScheduler {
-    fun submit(workManagerRequest: WorkManagerRequest)
+    /**
+     * Submits a new work request built from [workManagerRequestBuilder] to run in `WorkManager`.
+     */
+    suspend fun submit(workManagerRequestBuilder: WorkManagerRequestBuilder)
+
+    /**
+     * Checks if there are any pending requests scheduled for the provided [sessionId] and [requestType].
+     */
     fun hasPendingWork(sessionId: SessionId, requestType: WorkManagerRequestType): Boolean
-    fun cancel(sessionId: SessionId)
+
+    /**
+     * Cancel pending work requests for the session [SessionId].
+     * If [requestType] is provided, it will only cancel requests for that type, otherwise it will cancel all requests.
+     */
+    fun cancel(sessionId: SessionId, requestType: WorkManagerRequestType? = null)
 }
 
 fun workManagerTag(sessionId: SessionId, requestType: WorkManagerRequestType): String {