Should remove bean validations from core SDK

[fabiojose]

To provide a dependency-free SDK that can be used with a variety of frameworks and different versions.

I want to propose to remove the bean validations.

[cwallsfdc]

@fabiojose, we're running up against dependency conflicts w/ org.hibernate.validator which also brings in several other conflicting dependencies. This prevents us from upgrading to Cloudevent 1.0.

Is there a plan to replace org.hibernate.validator bean validation or removing altogether? Anyway to accelerate an alternative? We're happy to discuss and help.

[slinkydeveloper]

Solved by #108