replaced 31 with getClass().hashCode() for Entity hashCode

[pblanchardie]

Use getClass().hashCode() instead of 31 as Entity hashCode, as mentioned in #10097 (initially #8656).

I noticed that @Shaolans copied this implementation to EntityDTO.hashCode (commit 6a66c40), so I also updated it even if I'm not sure why it absolutely needs to be aligned, as DTOs don't have the same constraints as JPA Entities regarding equals and hashCode.

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[CLAassistant]

All committers have signed the CLA.

[mshima]

LGTM

[pblanchardie]

Please let me add a comment in the code before merging.

[DanielFran]

@pblanchardie Can you please add the comment so we can merge it?

[DanielFran]

Thanks @pblanchardie for the contribution

[DanielFran]

LGTM

[pascalgrimaud]

Missing unit tests here