Bypass macro attributes

[greyblake]

Context

Some derive traits can be customized with attributes (e.g. serde, garde, etc).

While at the moment it is possible to derive an arbitrary trait at own risk with derive_unsafe, the custom attributes are still ignored.

Specification

Bypass all the macro attribute associated with the type (see the examples in the associated issues below).

No extra validation needed for this, cause the attributes will be rejected by the rust compiler (if are not used by non of the traits).

This should address the following issues:

• Use with Garde #228
• Support serde attributes #201

[svenstaro]

I'd love to have this! I have a use case for this with sea_orm which also supports custom attributes but sadly I can't currently use it together with nutype because of this limitation. I'd be mega grateful if you could look at this sometime in the future. :)

[svenstaro]

Speaking of which, SeaORM has recently done pretty much this for their own use case: https://github.com/SeaQL/sea-orm/releases/tag/2.0.0-rc.32. Maybe something to take inspiration from?

[greyblake]

@svenstaro Thanks for the feedback! I'll try to make it read for the next release.