We can (theoretically) define any method on the blueprint that is non-default, and then add an implementation using custom methods.
This is currently not possible, as even though we get a warning the method is not valid, it is still added as an option candidate.

These methods should be warned and ignored.

Desired outcome:

[WARNING] Builder definition methods cannot have void return type (must be getters): io.helidon.builder.tests.custom.voidmethod.SomeTypeBlueprint.doSomething
[WARNING] Builder definition methods cannot have parameters (must be getters): io.helidon.builder.tests.custom.voidmethod.SomeTypeBlueprint.doSomething

Current outcome:
compilation of SomeType fails, because it has a void field.