Function otpauth_uri 

pub fn otpauth_uri(issuer: &str, account: &str, secret_b32: &str) -> String

Builds the otpauth:// URI an authenticator scans or imports.

The label is issuer:account and the issuer parameter repeats it, which is redundant by the spec and required in practice — several apps read only one of the two, and which one differs between them.