…h @ (fabpot)

This PR was merged into the 2.3 branch.

Discussion
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fixed YAML files missing quotes when a string starts with @

| 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

Commits
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e36fea8 fixed YAML files missing quotes when a string starts with @

This PR was squashed before being merged into the 2.3 branch (closes #5843).

Discussion
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Fixed the YAML syntax for service references

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | -

See symfony/symfony#16285 and symfony/symfony#16353 for context. I've just found two issues, but it's possible that this syntax is used in more places.

Commits
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daeda56 Fixed the YAML syntax for service references