Doctrine collections compatibility

[mnocon]

Follow-up to the discussion in #187

I've decided to use https://github.com/symfony/deprecation-contracts , because it provides a unified way to do deprecations. Also it's already a transitive dependency of this package:

symfony/config               v6.2.7     requires symfony/deprecation-contracts (^2.1|^3) 
symfony/console              v6.2.7     requires symfony/deprecation-contracts (^2.1|^3) 
symfony/dependency-injection v6.2.7     requires symfony/deprecation-contracts (^2.1|^3) 

[DonCallisto]

LGTM thanks

[mnocon]

Thank you!