Setup dependabot to update dependencies for Rust DRT code

[john-h-kastner-aws]

Category

Other

Describe the feature you'd like to request

We use dependabot for our library in cedar-policy/cedar, but there are also rust packages here which we should ideally keep up to date. We should probably start committing Cargo.lock files and having dependabot update them for the same reasons we did in this in main repo.

Describe alternatives you've considered

.

Additional context

No response

Is this something that you'd be interested in working on?

• 👋 I may be able to implement this feature request
• ⚠️ This feature might incur a breaking change

[john-h-kastner-aws]

PR did not quite work:

Dependabot couldn't fetch all your path-based dependencies

The affected dependencies were ../cedar/cedar-policy/Cargo.toml, ../cedar/cedar-policy-core/Cargo.toml, ../cedar/cedar-policy-validator/Cargo.toml, ../cedar/cedar-policy-formatter/Cargo.toml and ../cedar/cedar-testing/Cargo.toml.

To use path-based dependencies with Dependabot the paths must be relative, resolve to a directory in this project's source code, and contain a valid Rust project.
[Troubleshoot Dependabot errors](https://docs.github.com/github/managing-security-vulnerabilities/troubleshooting-dependabot-errors)

[john-h-kastner-aws]

Tried to fix with #502, but it didn't work