Initial support for member suggestions (#1631)

* Initial support for member suggestion (search and UI)

* Add custom `BottomSheetScaffold` implementation to workaround several scrolling bugs

* Start searching as soon as `@` is typed, add UI following initial designs

* Extract suggestion processing code

* Extract component, add previews, fix tests

* Add tests

* Add exception from kover to the forked bottom sheet code

* Add a feature flag for mentions

- Extract composer & mention suggestions to their composable.
- Extract mentions suggestions processing to its own class.
- Add `MatrixRoom.canTriggerRoomNotification` function.
- Update strings and conditions for displaying the `@room` mention.

---------

Co-authored-by: ElementBot <benoitm+elementbot@element.io>

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/room/FakeMatrixRoom.kt

@@ -71,6 +71,7 @@ class FakeMatrixRoom(
     override val alternativeAliases: List<String> = emptyList(),
     override val isPublic: Boolean = true,
     override val isDirect: Boolean = false,
+    override val isOneToOne: Boolean = false,
     override val joinedMemberCount: Long = 123L,
     override val activeMemberCount: Long = 234L,
     val notificationSettingsService: NotificationSettingsService = FakeNotificationSettingsService(),
@@ -106,6 +107,7 @@ class FakeMatrixRoom(
     private var progressCallbackValues = emptyList<Pair<Long, Long>>()
     private var generateWidgetWebViewUrlResult = Result.success("https://call.element.io")
     private var getWidgetDriverResult: Result<MatrixWidgetDriver> = Result.success(FakeWidgetDriver())
+    private var canUserTriggerRoomNotificationResult: Result<Boolean> = Result.success(true)
     val editMessageCalls = mutableListOf<Pair<String, String?>>()
 
     var sendMediaCount = 0
@@ -270,6 +272,10 @@ class FakeMatrixRoom(
         return canSendEventResults[type] ?: Result.failure(IllegalStateException("No fake answer"))
     }
 
+    override suspend fun canUserTriggerRoomNotification(userId: UserId): Result<Boolean> {
+        return canUserTriggerRoomNotificationResult
+    }
+
     override suspend fun sendImage(
         file: File,
         thumbnailFile: File,
@@ -434,6 +440,10 @@ class FakeMatrixRoom(
         canSendEventResults[type] = result
     }
 
+    fun givenCanTriggerRoomNotification(result: Result<Boolean>) {
+        canUserTriggerRoomNotificationResult = result
+    }
+
     fun givenIgnoreResult(result: Result<Unit>) {
         ignoreResult = result
     }