Automate starting a release process with release-plz

[cdunster]

We wish to create releases with as little human input as possible.

To start this release process we need a trigger that could be:

1. Creation of a release tag.
2. A merge of code changes into the main branch.
3. Manual trigger of a GitHub workflow.

Once started this process should:

• Check for SemVer compatible changes (maybe using cargo-semver-checks)
• Check for commits marked as breaking by conventional commits (following on from Enforce conventional commits and generate the changelog #116)
• Check or generate the changelog
• Bump the release version in the changelog and Cargo.toml

There is release-plz, an opinionated tool (or more of a collection of tools) that provides these features and needs to be examined to determine whether it is suitable.

There is cocogitto which is more fully featured and I think also does these things but needs looking into.

Depending on the approach, this may require a follow-on that finishes the release by merging the version bumps and changelog stuff into main and then builds and publishes the release artefacts to crates.io.

AC

• Use release-plz for this.