Fixing variable name for target_path
[Security] Fixed encoder reference
[Book][ServiceContainer] Added docs for YAML '@@' escaping

This PR deprecates https://github.com/symfony/symfony-docs/pull/2286

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes https://github.com/symfony/symfony/pull/7357
| Applies to    | 2.1
| Fixed tickets | https://github.com/symfony/symfony/issues/4889
[Security] Fix typo in chain provider entity
[Security] Used more explicit name
[Security] Fixed my_in_memory_provider
Merge pull request #2345 from Sgoettschkes/issue2253

Fixing variable name for target_path
Merge remote-tracking branch 'origin/2.1' into 2.1
[#2345] Minor tweaks to target path
Merge pull request #2349 from lyrixx/patch-ref-sercu

[2.1][Security] Fixed typo + some enhancement
Merge branch 'feature/di-parameter-escape' of github.com:tPl0ch/symfony-docs into tPl0ch-feature/di-parameter-escape

Conflicts:
	book/service_container.rst
Merge branch 'tPl0ch-feature/di-parameter-escape' into 2.1
Merge branch '2.1' into 2.2