Merge branch '2.8' into 3.4

* 2.8:
  Fix suggest.psr/*-implementation in composer.json files

Author: nicolas-grekas

composer.json

@@ -29,7 +29,7 @@
         "psr/log": "~1.0"
     },
     "suggest": {
-        "psr/container": "To instantiate the Security class",
+        "psr/container-implementation": "To instantiate the Security class",
         "symfony/event-dispatcher": "",
         "symfony/http-foundation": "",
         "symfony/validator": "For using the user password constraint",