Remove messages entries that are only ever served by another domain

[Vondry]

Third of the PRs splitting up #3753. Independent of the others—it branches from master and touches only the messages catalogues.

This is a pure cleanup with no behavioural impact: 24 unreachable translation units are removed, with no lookup changes and no translated wording altered.

The four keys

Each of these keys exists in the messages domain but is only ever resolved from a different translation domain:

Key	Used at	Resolved in
user.not_valid_display_name	src/Entity/User.php:35,36 (Assert\NotBlank, Assert\Length)	validators
user.not_valid_email	src/Entity/User.php:49 (Assert\Email)	validators
user.not_valid_password	src/Entity/User.php:57 (Assert\Length)	validators
You have to login in order to access this page.	src/Security/AuthenticationEntryPointRedirector.php:26 (trans(..., 'security'))	security

These five call sites are the only occurrences anywhere in the repository, including vendor/. Nothing resolves these keys from the messages domain, and debug:translation --domain=messages reports all four as unused.

Why the messages copies cannot matter

validator.translation_domain is configured as validators (verified with debug:container and not overridden in framework.yaml), and ExecutionContext:145 translates every validation message in that domain.

Symfony's Translator supports fallback locales, but not fallback domains. A lookup in the validators domain can never fall back to messages.

These entries are therefore unreachable by construction, not merely unused.

What is removed (and what is not)

Entries are removed only where the same locale already contains the key in the domain that actually serves it.

Locale	Removed	Left in place
cs, en, ru	4 each	—
el, tr, uk	3 each	—
fr	3	You have to login…
hu	—	2
nl	—	3
zh_CN	—	3

24 translation units are removed across 7 files; 9 are intentionally retained.

The remaining entries correspond to locales where the serving domain does not yet contain the translation (security.fr, security.nl, validators.hu, validators.nl, and validators.zh_CN). Those locales currently fall back to English.

Although the duplicate entries in messages are equally unreachable, deleting them would discard translated text that should instead be moved into the correct domain. That would change runtime behaviour and is therefore left for a separate PR.

[bobvandevijver]

Strictly speaking, this is classified as a breaking change. We do not know what our consumers are using, and that could result in them no longer having a translation.

For this change, we will need to target 6.2, and add a note to the upgrade notes (which translations have been removed).

By targeting the 6.2 branch, the translations that were kept because they need to be removed can then also be done in the same (this) PR.

[bobvandevijver]

By the way, I've just update 6.2 so that the latest translation updates for 6.1 are available there now as well.