The `Debug` implementation for secrets is feature gated on `std` because
it uses a hasher from `std`. If `bitcoin_hashes` is enabled we can use
it for hashing. If neither `std` nor `bitcoin_hashes` is enabled fall
back to outputting:
<secret requires std or bitcoin_hashes feature to display>
Remove the docs conditional since we now implement `Debug` always.
Rustc can warn us when we forget to add `Copy` and `Deubg` trait
implementations to types.
Add lint directives to enable warnings for missing `Copy` and `Debug`
implementations. Use the newly emitted warnings to find types that do
not implement our 'standard' traits. These 'standard' traits are defined
as the set of attributes that it has been found beneficial to
opportunistically add to all types, these are
- Copy
- Clone
- Debug
- PartialEq and Eq
- PartialOrd and Ord
- Hash
This documents the Cargo features making sure docs.rs shows warning for
feature-gated items. They are also explicitly spelled out in the crate
documentation.