[Process] Use correct test for empty string in UnixPipes
[Process] Fix unit tests on Windows platform
[Process] Adjust PR #11264, make it Windows compatible and fix CS
minor #11397 [2.3][Process] Fix unit tests on Windows platform (romainneutron)

This PR was merged into the 2.3 branch.

Discussion
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[2.3][Process] Fix unit tests on Windows platform

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT

Commits
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d418935 [Process] Fix unit tests on Windows platform
bug #11381 [2.3] [Process] Use correct test for empty string in UnixPipes (whs, romainneutron)

This PR was merged into the 2.3 branch.

Discussion
----------

[2.3] [Process] Use correct test for empty string in UnixPipes

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

This PR supersedes #11264 : 2.3 compatibility + Windows compatibility + CS fix

Commits
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cec0a45 [Process] Adjust PR #11264, make it Windows compatible and fix CS
9e1ea4a [Process] Use correct test for empty string in UnixPipes
[Translator][FrameworkBundle] Added @ to the list of allowed chars in Translator
bug #11403 [Translator][FrameworkBundle] Added @ to the list of allowed chars in Translator (takeit)

This PR was squashed before being merged into the 2.3 branch (closes #11403).

Discussion
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[Translator][FrameworkBundle] Added @ to the list of allowed chars in Translator

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11396
| License       | MIT

Commits
-------

3176f8b [Translator][FrameworkBundle] Added @ to the list of allowed chars in Translator
[Validator] Backported #11410 to 2.3: Object initializers are called only once per object
bug #11411 [Validator] Backported #11410 to 2.3: Object initializers are called only once per object (webmozart)

This PR was merged into the 2.3 branch.

Discussion
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[Validator] Backported #11410 to 2.3: Object initializers are called only once per object

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Before, object initializers were called multiple times if an object was validated in different groups in the same validation run. The initializers, however, are not aware of the current validation group, so calling them more than once does not make sense.

Now, object initializers are called exactly once per validated object.

See #11410

Commits
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291cbf9 [Validator] Backported #11410 to 2.3: Object initializers are called only once per object