Improve audio focus management (#4707)

* Extract Audio focus management to its own modules.

* Request Audio focus when playing a voice message.

* Add missing dependency.
(and remove a duplicated one)

* Request Audio focus when playing a video/audio in the media viewer.

* Pause audio when audio focus is lost.

* Rename class

* Fix tests

* Fix detekt issue.

* Audio focus: let the system handle automatic ducking when playing media.

* Document and update API

* Remove useless space.

libraries/audio/api/build.gradle.kts

@@ -0,0 +1,13 @@
+/*
+ * 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.
+ */
+plugins {
+    id("io.element.android-library")
+}
+
+android {
+    namespace = "io.element.android.libraries.audio.api"
+}

libraries/audio/api/src/main/kotlin/io/element/android/libraries/audio/api/AudioFocus.kt

@@ -0,0 +1,32 @@
+/*
+ * 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.audio.api
+
+enum class AudioFocusRequester {
+    ElementCall,
+    VoiceMessage,
+    MediaViewer,
+}
+
+interface AudioFocus {
+    /**
+     * Request audio focus for the given requester.
+     * @param requester The mode for which to request audio focus.
+     * @param onFocusLost Callback to be invoked when the audio focus is lost.
+     * @return true if the audio focus was successfully requested, false otherwise.
+     */
+    fun requestAudioFocus(
+        requester: AudioFocusRequester,
+        onFocusLost: () -> Unit,
+    )
+
+    /**
+     * Release the audio focus.
+     */
+    fun releaseAudioFocus()
+}