#27345 Added note about MongoDbStore's dependancy on mongodb/mongodb

Author: Joe Bennett

components/lock.rst

@@ -223,7 +223,8 @@ support blocking, and expects a TTL to avoid stalled locks::
 MongoDbStore
 ~~~~~~~~~~~~
 
-The MongoDbStore saves locks on a MongoDB server, it requires a ``\MongoDB\Client`` connection.
+The MongoDbStore saves locks on a MongoDB server, it requires a ``\MongoDB\Client``
+connection from `mongodb/mongodb`_.
 This store does not support blocking, and expects a TTL to avoid stalled locks::
 
     use Symfony\Component\Lock\Store\MongoDbStore;
@@ -473,10 +474,8 @@ this is ``_id`` which already has a unique index being the collection identifier
 It is strongly recommended to leave this as is. If you do need to change the
 ``<resource_field>`` you **MUST** ensure you place a unique index on your filed.
 
-It's possible to automatically expire the locks in the database as described below:
-
-A TTL index can be used on MongoDB 2.2+ to cleanup expired locks
-automatically. Such an index can for example look like this:
+A TTL index can be used on MongoDB 2.2+ to cleanup expired locks automatically.
+Such an index can for example look like this:
 
 .. code-block:: javascript
 
@@ -560,3 +559,4 @@ are still running.
 .. _`locks`: https://en.wikipedia.org/wiki/Lock_(computer_science)
 .. _Packagist: https://packagist.org/packages/symfony/lock
 .. _`PHP semaphore functions`: http://php.net/manual/en/book.sem.php
+.. _`mongodb/mongodb`: https://packagist.org/packages/mongodb/mongodb