HTTP Problem-based Error Handling Library

This crate provides a general mechanism for error handling based on the RFC 7807 problem entity with the Problem type.

Users can find many pre-defined errors at the http and sql modules.

The workflow for error handling with this library is as follow:

1. Use the predefined errors/functions or define a new one with the define_custom_type! macro to returns errors in functions that return Result<T, Problem> (an alias is provided in the library).
   • You can also use the extensions traits ResultExt, ProblemResultExt, OptionExt to handle common cases.
2. Catch any desired error with ProblemResultExt::catch_err.