This commit refactors the test suites for the `crypt` and `trix` packages to follow the Good, Bad, and Ugly testing strategy.
- `_Good` tests cover the ideal "happy path" scenarios.
- `_Bad` tests cover expected failure scenarios with well-formed but invalid inputs.
- `_Ugly` tests cover malicious or malformed inputs designed to cause crashes or panics.
This new testing structure makes the test suite more organized, comprehensive, and robust.
Additionally, this commit includes a bug fix for the `Luhn` function, which now correctly handles empty and single-digit strings.
This commit introduces a new, generic `.trix` file format, which is decoupled from any specific encryption algorithm.
The format is defined in `docs/trix_format.md` and consists of a magic number, version, a flexible JSON header, and a raw data payload.
A new `trix` Go package is implemented to handle the encoding and decoding of this format. Unit tests are included to verify the implementation.
An example file, `examples/main.go`, is also added to demonstrate how to use the `.trix` container to store data encrypted with the `chachapoly` package, showcasing the intended decoupled design.
