[Serializer] Add documentation about a new XmlEncoder CDATA wrapping opt-out context option

[AndoniLarz]

Add documentation of https://github.com/symfony/symfony/pull/49893 which has been merged in 6.4.

TODO :

• [x] Fix conflicts (by rebasing)
• [x] Edit the context option name (enable_cdata_wrapping => cdata_wrapping)
• [x] Wait for the reviews

[AndoniLarz]

Hi @xabbuh @OskarStark , I fixed the conflicts and updated the context option name following the code that has been merged. Does it look good to you ?

[OskarStark]

Please target 7.1 branch for now, thanks

[AndoniLarz]

Please target 7.1 branch for now, thanks

Even though the feature has been added in 6.4 ?

[OskarStark]

Even though the feature has been added in 6.4 ?

Ah sorry this is about another option. Sorry I mixed things up. No in this car 6.4 is fine, but a versionadded would be helpful at all:

.. versionadded:: 6.4

    The `cdata_wrapping` option was introduced in Symfony 6.4.

[AndoniLarz]

Even though the feature has been added in 6.4 ?

Ah sorry this is about another option. Sorry I mixed things up. No in this car 6.4 is fine, but a versionadded would be helpful at all:

.. versionadded:: 6.4

    The `cdata_wrapping` option was introduced in Symfony 6.4.

Alright no problem. I'll make the changes soon

[OskarStark]

Open for finishing this PR by handling my comments?

[AndoniLarz]

Open for finishing this PR by handling my comments?

It should be good now :smile:

[OskarStark]

Thank you Andoni and congratulations on your first contribution to the Symfony documentation 🎉