refactor v1, start support for more protocols and implement nak

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

internal/outpost/radius/eap/protocol/packet.go

@@ -3,11 +3,9 @@ package protocol
 type Payload interface {
 	Decode(raw []byte) error
 	Encode() ([]byte, error)
+	Handle(ctx Context) Payload
+	Type() Type
+	Offerable() bool
 }
 
 type Type uint8
-
-const (
-	TypeIdentity     Type = 1
-	TypeMD5Challenge Type = 4
-)