pub fn validate_verifier(code_verifier: &str) -> Result<(), PkceError>Expand description
Validate a code_verifier against RFC 7636 §4.1’s syntax.
43 <= len <= 128, and every character in the unreserved set
[A-Za-z0-9-._~]. Enforced on the way in: a verifier that cannot have been
produced by a conforming client is not worth hashing.