feat: Add methods to load all room keys from online key backup

This makes it possible to load
and sync all room keys
right after the bootstrap if the
app wants to do this.

lib/encryption/key_manager.dart

@@ -667,6 +667,31 @@ class KeyManager {
     }
   }
 
+  /// Loads and stores all keys from the online key backup. This may take a
+  /// while for older and big accounts.
+  Future<void> loadAllKeys() async {
+    final info = await getRoomKeysBackupInfo();
+    final ret = await client.getRoomKeys(info.version);
+    await loadFromResponse(ret);
+  }
+
+  /// Loads all room keys for a single room and stores them. This may take a
+  /// while for older and big rooms.
+  Future<void> loadAllKeysFromRoom(String roomId) async {
+    final info = await getRoomKeysBackupInfo();
+    final ret = await client.getRoomKeysByRoomId(roomId, info.version);
+    final keys = RoomKeys.fromJson({
+      'rooms': {
+        roomId: {
+          'sessions': ret.sessions.map((k, s) => MapEntry(k, s.toJson())),
+        },
+      },
+    });
+    await loadFromResponse(keys);
+  }
+
+  /// Loads a single key for the specified room from the online key backup
+  /// and stores it.
   Future<void> loadSingleKey(String roomId, String sessionId) async {
     final info = await getRoomKeysBackupInfo();
     final ret =

test/encryption/online_key_backup_test.dart

@@ -72,6 +72,30 @@ void main() {
           true);
     });
 
+    test('Load all Room Keys', () async {
+      if (!olmEnabled) return;
+      const roomId = '!726s6s6q:example.com';
+      const sessionId = 'ciM/JWTPrmiWPPZNkRLDPQYf9AW/I46bxyLSr+Bx5oU';
+      await client.encryption!.keyManager.loadAllKeysFromRoom(roomId);
+      expect(
+          client.encryption!.keyManager
+                  .getInboundGroupSession(roomId, sessionId) !=
+              null,
+          true);
+    });
+
+    test('Load all Keys', () async {
+      if (!olmEnabled) return;
+      const roomId = '!726s6s6q:example.com';
+      const sessionId = 'ciM/JWTPrmiWPPZNkRLDPQYf9AW/I46bxyLSr+Bx5oU';
+      await client.encryption!.keyManager.loadAllKeys();
+      expect(
+          client.encryption!.keyManager
+                  .getInboundGroupSession(roomId, sessionId) !=
+              null,
+          true);
+    });
+
     test('upload key', () async {
       if (!olmEnabled) return;
       final session = olm.OutboundGroupSession();