proper enum schema for pydantic

[jbkoh]

Summary

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
  • This change has an associated test.
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
  • It might be breaking anybody using int instead of Enum when using pydantic, though I don't think that's desired.
• This PR is not a code change (e.g. documentation, README, ...)

[jbkoh]

just added a test too.

[jbkoh]

@Gobot1234 please review and let me know if it's in the right direction.

[Gobot1234]

Having a function for each of these adds a lot of bulk to the generated files, can this not go in the original definition for Enum and also be inlined into a lambda as this doesn't need type hints?

[jbkoh]

I'm fine with the suggestion. Where do you recommend to declare the validate function? We can also define it as a method in betterproto library too.

[jbkoh]

something like

def get_validate_betterproto_enum(cls):
  def validate(cls, value): 
    return cls(value)
  return validate