v0.3.1

v0.3.1 — MSRV correction

Same code as v0.3.0 (see its release notes for the full list of security and correctness fixes) with the declared minimum toolchain lowered from 1.88 to 1.83, so downstream builds on older compilers (the R package on CRAN, rustc 1.86) can consume the crate. Two standard-library calls introduced in 1.87/1.82 were replaced with plain equivalents; no behavioural change.

The committed Cargo.lock still resolves newer transitive releases (time 0.3.49, p12-keystore 0.2.1) that require 1.88; consumers on older toolchains pin those (time = 0.3.45, p12-keystore = 0.2.0), which is what the R package does.

This is the version published to crates.io.