• Refactor some code in preparation for the logs integration
• No breaking changes
• Improve the docs a little
• Test that a breadcrumb with errors carries the stringified error chain, behavior we added in refactor(tracing): remove EventFilter::exception and always attach exception #768
• It's also a behavioral change because we were previously attaching all error fields in an errors field in the JSON data of the breadcrumb, which doesn't make much sense. Now we'll store them in separate fields, retaining the original name

example:

            tracing::info!(
                database_error = &db_error as &dyn Error,
                parse_error = &parse_error as &dyn Error,
                retry_count = 3,
                connection_timeout = "30s",
                "Multiple errors occurred during database operation"
            );

Before:

After: