Add typed error method to challenges

[nckslvrmn]

Per RFC 8555 §7.1.6 and §8.2, when a challenge fails validation the CA sets status: "invalid" and includes an error field with the same problem document format (type, detail) used in HTTP error responses. Currently the gem stores this as a raw hash, requiring consumers to manually parse it and map type to the correct error class — duplicating the same logic the gem already uses internally for HTTP-level errors.

Changes

• Added typed_error method to Acme::Client::Resources::Challenges::Base
• Uses the existing ACME_ERRORS mapping to return a properly typed error instance (e.g. Acme::Client::Error::Dns, Acme::Client::Error::Unauthorized)
• Falls back to Acme::Client::Error for unknown error types
• Returns nil when no error is present
• The existing error attr (raw hash) is unchanged

Usage

challenge.reload

if challenge.status == 'invalid'
  err = challenge.typed_error
  case err
  when Acme::Client::Error::Dns
    # transient DNS failure, maybe retry
  when Acme::Client::Error::Caa
    # CAA prevents issuance, don't retry
  end
end

No breaking changes

Purely additive. The raw error hash continues to be available as before.

[unixcharles]

You could switch on error['type'] too but I could see the user wanting to raise the error too.