…tao/core#8843).

Description
-----------

The Contao DataCollector used an outdated method for referencing templates which
seen to have been remove recently. Update to the modern @-prefixed way of referencing
templates.

Fixes the following error (occures when opening the debugger, or even just show the debug toolbar).

```
The profiler template "ContaoCore:Collector:contao.html.twig" for data collector "contao" does not exist.

UnexpectedValueException
in vendor/symfony/symfony/src/Symfony/Bundle/WebProfilerBundle/Profiler/TemplateManager.php (line 108)
```

> In the past, Symfony used a different syntax to refer to templates. This format, which uses colons (:) to separate each template path section, is less consistent and has worse performance than the Twig syntax. (https://symfony.com/doc/3.4/templating/namespaced_paths.html)

> [...] but you must prefix the @ character when using it in templates (that's how Twig can differentiate namespaces from regular paths). (https://symfony.com/doc/current/templating/namespaced_paths.html)

There is one open question (thus tagged as RFC). It does seem to work in the managed edition. Any idea why?

Commits
-------

b7b6027 Fix namespaced paths in Contao DataCollector
0fc0da7 Fixed test so it expects the correct template again.

…1390).

Description
-----------

Otherwise the main request will never allow for client cache as it takes the lowest value of all fragments (which is 0 at the moment for us).

Commits
-------

e1602c2 Make sure insert tags get the same client cache time as the page settings
eb0932b CS

Description
-----------

This PR fixes #1283.

Symfony has recently changed their session listener to always make the response private if the session has been started. Although we agree with the change, it renders the HTTP cache unusable, because Contao always starts a session (e.g. to store the user's language). This PR decorates the Symfony session listener and circumvents Symfony's changes by not making the response private if the request is a Contao front end request.

Of course, our long term goal should be to adjust Contao so it only starts a session if it really has to.

Commits
-------

6ecc514 Set the front end response cache headers in an event listener (see #1283).
f937aaf Fix the copyright notice.
99ad48d Do not make the response private when saving the session (see #1388).
41580e2 Add the unit tests.
e967856 Add a description to the session listener.

…ccess the "user" module (see #1309).

…fferent versions.

…ethod (see #1402).