Unexpected `diagnostic` field attributes accepted

[john-h-kastner-aws]

Given a structure deriving Diagnostic with an unexpected field attribute #[diagnostic(bogus)], I expect that miette would report an error but it does not. The following struct compiles without error, simply ignoring the attribute.

use miette::Diagnostic;
use thiserror::Error;
#[derive(Diagnostic, Error, Debug)]
#[error("")]
struct E {
    #[diagnostic(bogus)]
    i: i32
}

This is particularly problematic when the attribute is in fact supported on records. For example, if a field is annotated with #[diagnostic(transparent)], it feels reasonable to think it will forward the diagnostic impl to that field, but instead the annotation is silently ignored.

#[derive(Diagnostic, Error, Debug)]
#[error("")]
struct E2 {
    #[diagnostic(transparent)]
    e: E
}

This specifically lead to a bug in our library where some errors where missing source labels and help messages.