* simplify the code generated for unit enums
* simplify generated code for validating object properties
* optimize internal and externally tagged enums
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Co-authored-by: Robin Appelman <robin@icewind.nl>
Default values that don't implement Serialize are now ignored, rather than causing a compile error.
This is done by simulating specialization using a technique copied from Rocket:
5ebefa97c9/core/lib/src/sentinel.rs (L391-L445)Fixes#115
Previously whenever a field with a default value has both `skip_serializing_if` and `with`/`serialize_with` attributes, the value would be converted to a type that performs the custom serialization before checking if it should be serialized. This would cause the wrong type to be given to the skip_serializing_if function, causing a compile error.
Issue #26
