feat: add support for error codes

[hf]

Adds support for error codes. All AuthError descendants will now have a code property which will encode (when present and supported by the server) the reason why the error occurred.

To support this, the library will now advertise X-Supabase-Api-Version: 2024-01-01 which is the first version of a new versioning strategy that supports a different encoding for error responses.

See:

• https://github.com/supabase/gotrue/pull/1377