[PLATFORM-833]: Add a way of using the Display implementation instead of the Debug implementation when redacting

[WilliamVenner]

https://prima-assicurazioni-spa.myjetbrains.com/youtrack/issue/PLATFORM-833

This PR implements the #[redact(display)] option which allows the user to override which format implementation is chosen to redact.

This allows users to choose redacting the output of a type's std::fmt::Display implementation where they feel is appropriate.

Relevant Slack discussion https://prima.slack.com/archives/C01C70U9F37/p1670860264520579

[oliverbrowneprima]

Could you add some tests that include macro invocation with display in here?

[WilliamVenner]

@oliverbrowneprima Uhh yeah is the test in redaction_tests.rs not enough?

[oliverbrowneprima]

I'd prefer, for the sake of avoiding regressions in the future, if there was also:

• Redacted Display on a struct with named members
• Redacted Display on an enum
• A case that actually redacts some data (e.g. make that string contain something)
• A case that derives both a redacted Display and Debug, and asserts they work as expected (with some actual redaction occuring)

[cpiemontese]

Really nice, I agree on adding a few more test cases which capture how we expect this to behave

[WilliamVenner]

Cheers guys, caught somewhere where #[redact(display)] shouldn't be 🙂