feat(webauthn): credential message pack (#660)

This allows storing credentials with MessagePack.

Author: james-d-elliott

webauthn/authenticator.go

@@ -4,26 +4,30 @@ import (
 	"github.com/go-webauthn/webauthn/protocol"
 )
 
+//go:generate msgp
+
+//msgp:replace protocol.AuthenticatorAttachment with:string
+
 // Authenticator represents a specific authenticator in the context of a [Credential].
 type Authenticator struct {
 	// The AAGUID of the authenticator. An AAGUID is defined as an array containing the globally unique
 	// identifier of the authenticator model being sought.
-	AAGUID []byte `json:"AAGUID"`
+	AAGUID []byte `json:"AAGUID" msg:"aaguid"`
 
 	// SignCount is a representation of the number of times the Authenticator or Credential have been used to login.
 	// Upon a new login operation, the Relying Party compares the stored signature counter value with the new SignCount
 	// value returned in the assertion’s authenticator data. If this new SignCount value is less than or equal to the
 	// stored value, a cloned authenticator may exist, or the authenticator may be malfunctioning.
-	SignCount uint32 `json:"signCount"`
+	SignCount uint32 `json:"signCount" msg:"sc"`
 
 	// CloneWarning is a signal that the authenticator may be cloned, i.e. at least two copies of the
 	// credential private key may exist and are being used in parallel. Relying Parties should incorporate
 	// this information into their risk scoring. Whether the Relying Party updates the stored signature
 	// counter value in this case, or not, or fails the authentication ceremony or not, is Relying Party-specific.
-	CloneWarning bool `json:"cloneWarning"`
+	CloneWarning bool `json:"cloneWarning" msg:"cw"`
 
 	// Attachment is the authenticatorAttachment value returned by the request.
-	Attachment protocol.AuthenticatorAttachment `json:"attachment"`
+	Attachment protocol.AuthenticatorAttachment `json:"attachment" msg:"aa"`
 }
 
 // SelectAuthenticator is a convenience function that constructs a [protocol.AuthenticatorSelection] from individual