fixes environment/application mistake
Link to FOSHttpCacheBundle
feature #4175 Link to FOSHttpCacheBundle (ddeboer)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #4175).

Discussion
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Link to FOSHttpCacheBundle

* Link to FOSHttpCacheBundle that can help with cache invalidation.
* Qualify the strong negative opinion about cache invalidation, which we also find in the [Cache Invalidation section](http://symfony.com/doc/current/book/http_cache.html#http-cache-invalidation) in the docs. The cookbook (and docs) are too opiniated on this subject and offer no balanced view. We should not forget that [RFC 2616](http://tools.ietf.org/html/rfc2616#section-13.10) considers invalidation seriously. I would love to hear from the original  authors of this doc section or any others what their arguments against invalidation are. Let’s try to introduce both benefits and drawbacks more carefully in the docs (e.g., as is done [here](http://foshttpcache.readthedocs.org/en/latest/invalidation-introduction.html)).

Commits
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9243612 Link to FOSHttpCacheBundle
minor #4178 [Cookbook][Configuration] fixes environment/application mistake (dyferencjal)

This PR was merged into the 2.3 branch.

Discussion
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[Cookbook][Configuration] fixes environment/application mistake

IMO enviroment isn't properly used here. It should be application.

Commits
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6ab9c16 fixes environment/application mistake
Route description correction.

The actual route is '/random/{limit}' and not '/number/{limit}'.
(cherry picked from commit 0a4511345a82313cb6cc5fc0dae1351073f50c6a)
Merge branch '2.3' into 2.4

* 2.3:
  Route description correction.
  Link to FOSHttpCacheBundle
  fixes environment/application mistake