merged branch drak/session_flashmessages (PR #3267)

Commits
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5ae76f1 [HttpFoundation] Update documentation.
910b5c7 [HttpFoudation] CS, more tests and some optimization.
b0466e8 [HttpFoundation] Refactored BC Session class methods.
84c2e3c [HttpFoundation] Allow flash messages to have multiple messages per type.

Discussion
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[2.1][HttpFoundation] Multiple session flash messages

Bug fix: no
Feature addition: yes
Backwards compatibility break: yes, but this already happened in #2583.  BC `Session` methods remain unbroken.
Symfony2 tests pass: yes
Fixes the following tickets: #1863
References the following tickets: #2714, #2753, #2510, #2543, #2853
Todo: -

This PR alters flash messages so that it is possible to store more than one message per flash type using the `add()` method or by passing an array of messages to `set()`.

__NOTES ABOUT BC__

This PR maintains BC behaviour with the `Session` class in that the old Symfony 2.0 methods will continue to work as before.

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by drak at 2012-02-13T06:28:33Z

I think this is ready for review @fabpot @lsmith77

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by lsmith77 at 2012-02-14T19:30:39Z

the FlashBag vs. AutoExpireFlashBag behavior and setup difference should probably also be explained in the upgrading log

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by drak at 2012-02-15T04:43:14Z

@lsmith77 Those differences are explained already in the changelog

 * Added `FlashBag`. Flashes expire when retrieved by `get()` or `all()`.
   This makes the implementation ESI compatible.
 * Added `AutoExpireFlashBag` (default) to replicate Symfony 2.0.x auto expire behaviour of messages auto expiring
   after one page page load.  Messages must be retrived by `get()` or `all()`.

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by Crell at 2012-02-19T17:35:34Z

Drak asked me to weigh in here with use cases.  Drupal currently has a similar session-stored-messaging system in place that I'd like to be able to replace with Flash messages.  We frequently have multiple messages within a single request, however, so this change is critical to our being able to do so.

For instance, when saving an article in Drupal there is, by default, a "yay, you saved an article!" type message that gets displayed.  If you also have the site configured to send email when a post is updated, you may see a "email notifications sent" message (depending on your access level).  If you have a Solr server setup for search, and you're in debug mode, there will also be a "record ID X added to Solr, it should update in 2 minutes" message.  And if there's a bug somewhere, you'll also get, as an error message rather than notice message, a "Oops, E_NOTICE on line 54" message.

Form validation is another case.  If you have multiple errors in a single form, we prefer to list all of them.  So if you screw up 4 times on a form, you may get 4 different error messages showing what you screwed up so you can fix it in one go instead of several.

Now sure, one could emulate that by building a multi-message layer on top of single-layer messages, but, really, why?  "One is a special case of many", and there are many many cases where you'll want to post multiple messages.  Like, most of Drupal. :-)

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by lsmith77 at 2012-03-06T20:55:51Z

@fabpot is there any information you still need before merging this? do you want more discussion in which case you might want to take this to the mailing list ..

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by drak at 2012-03-08T18:54:13Z

Another plus for this PR is that it requires no extra lines of code in templates etc to display the flashes, see https://github.com/symfony/symfony/pull/3267/files#diff-1

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by drak at 2012-03-15T06:38:21Z

Rebased against current `master`, should be mergeable again..

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by evillemez at 2012-03-17T03:08:41Z

+1 to this, I have an extended version of HttpFoundation just for this... would love to get rid of it.
[HttpFoundation] fixed a test
tweaked UPGRADE file