Type suggestions and validations for avro enum types

[arkadius]

Would be nice to have type sugestions or at least type validation for enum types. There are few mechanisms that can be used for that for now:

1. We can provide dynamic dictionaries for all enum types and then expression will look like: #input.someEnumValue == #avro_enum.someEnum['first value']
2. If we will have additional metadata in literals with value, we can declare that type is union of literal values and then just write #input.someEnumValue == 'mismatch value'. Suggestions won't work, but thanks to dynamic expression validation we will got message like type 'mismatch value' cann't be subclass of 'first value' | 'second value'. Type metadata could be useful also for other things like meta property with avro schema for better validation that writer schema is compatible with reader schema.