Update the release process to explain how to update the crate along with the main CBMC version

Author: NlightNFotis

doc/ADR/release_process.md

@@ -1,7 +1,7 @@
 \page release-process Release Process
 
 **Date**: 2020-10-08
-**Updated**: 2022-06-23
+**Updated**: 2023-03-29
 **Author**: Fotis Koutoulakis, fotis.koutoulakis@diffblue.com
 **Domain**: Release & Packaging
 
@@ -10,7 +10,11 @@
 The current process we follow through to make a new release is the following:
 
 1. At the point in time we want to make the release, we make a change to
-   `src/config.inc`, and update the configuration variable `CBMC_VERSION`.
+   two files: `src/config.inc`, wherein we update the configuration variable
+   `CBMC_VERSION`, and `src/libcprover-rust/Cargo.toml`, wherein we update
+   the `version` variable to be the same as `CBMC_VERSION` (e.g. set both
+   to `5.80.0`).
+
    This is important as it informs the various tools of the current version
    of CBMC.
 
@@ -22,6 +26,19 @@ The current process we follow through to make a new release is the following:
    denoting the minor version, and `z` identifying the patch version (useful
    for a hotfix or patch.)
 
+3. Pushing the Rust crate, which is documented [here](https://doc.rust-lang.org/cargo/commands/cargo-publish.html)
+   but effectively entails logging in with an API token generated from
+   https://crates.io with `cargo login`, and then issuing `cargo publish`.
+
+   The usual environment variables are required (part of the `publish`
+   step is that the crate can be built) - these are documented in the
+   `readme.md` file at the root of the `src/libcprover-rust/` directory,
+   and online at [libcprover_rust](https://crates.io/crates/libcprover_rust).
+
+   For the crate to be pushed successfully, the user performing the `cargo
+   publish` step needs to be a member of the [diffblue/diffblue-opensource](https://github.com/orgs/diffblue/teams/diffblue-opensource)
+   team.
+
 At this point, the rest of the process is automated, so we don't need to do
 anything more, but the process is described below for reference:
 
@@ -63,6 +80,24 @@ detectable change including bugfixes can do that. Instead, major version
 increments should signal that we expect many users will have to review their
 workflows for potential breakages, not just any.
 
+### Rust API versioning
+
+Following discussions during the development of `libcprover_rust`, it was decided
+that it would be easiest if the Rust API version was following the same scheme
+that CBMC does, so that it's clear which version of the Rust API corresponds to
+which version of CBMC.
+
+This means that the Rust API has two "versions" it can report.
+
+1. The library version, as reported in `Cargo.toml`, and
+2. The (C++) API version, which is coming from CBMC and aligns with the version
+   number in `config.inc` (reported via the `get_api_version()` API call).
+
+Most of the time, these two numbers will be the same - but there can be scenarios
+where they can diverge: if the user for example uses a later version of the
+Rust API (say, `5.80.0`) to link against a static library representing an older
+version of CBMC (say `5.79.0`).
+
 ## Constraints
 
 Initial design of the release process suggested that the release cadence