We have a lot of backend types leaking via the public API, including
e.g. `FieldElement51`:
https://docs.rs/curve25519-dalek/latest/curve25519_dalek/backend/serial/u64/field/struct.FieldElement51.html
At the very least, these types shouldn't be visible in the rustdoc.
This PR hides them from the docs, but ideally we would hide them
completely from the public API (which might technically be considered a
breaking change, but IMO leaking them at all is a bug).
Adds a lints section to the top of lib.rs with the following:
#![warn(
clippy::unwrap_used,
missing_docs,
rust_2018_idioms,
unused_lifetimes,
unused_qualifications
)]
`warn` is used instead of `deny` to prevent the lints from firing during
local development, however we already configure `-D warnings` in CI so
if any lint fails on checked-in code, it will cause a CI failure.
This commit also fixes or explicitly allows any current violations of
these lints. The main ones were:
- `clippy::unwrap_used`: replaces usages of `unwrap` with `expect`
- `rust_2018_idioms`: no implicit lifetimes, which were present on
usages of `core::fmt::Formatter`
