CHANGES.md

Changes for the 2022 rewrite / reorginzation / expansion:

1. All examples updated to Rust edition 2021, and the latest stable versions of the crates.
2. All example code moved to actual .rs files. All examples are runnable inside the project via cargo run --example, and 100% of the examples are also run via cargo test. This makes it easier for users to run the examples that are incompatible with the Rust Playground because they interact with the filesystem, or a database, etc.. Modifying and running the examples on the command line shall be encouraged.
3. As a consequence of the above, elimination of the skeptic crate to test code within the Markdown files. Source code for the examples is brought in by the {{#include examples/foobar.rs}} Markdown directive.
4. The code is organized as a series of workspaces. This also avoids the problem with the skeptic based test system which would sometimes link in the incorrect version of a crate for a particular codebase. All the workspaces share the same target directory, which should reduce compilation times.
5. No hiding of details. All code presented as full and complete. The documentation should explain any details needed to understand the example.
6. Remove use of error-chain crate. This has been replaced with the simpler use of Result<(), Box<dyn Error>> or similar in the examples. There will be an extended section on using anyhow and thiserror as well. See also: https://nick.groenen.me/posts/rust-error-handling/
7. As a consequence of the above, updating to the current stable versions of crates is as easy as running cargo update and then running cargo test to identify any API changes. If everything works, then cargo upgrade --workspace can be used to insert the updated crate versions into the Cargo.toml files. This should be done frequently, so that the Cookbook shows examples that are correct for the current stable versions of crates.