module-transaction: Add support for binary conversations

A module can now initiate a binary conversation decoding the native
pointer value as it wants.

Added tests to verify the main cases

cmd/pam-moduler/tests/integration-tester-module/serialization.go

@@ -36,6 +36,16 @@ type SerializableStringConvResponse struct {
 	Response string
 }
 
+// SerializableBinaryConvRequest is a serializable binary request.
+type SerializableBinaryConvRequest struct {
+	Request []byte
+}
+
+// SerializableBinaryConvResponse is a serializable binary response.
+type SerializableBinaryConvResponse struct {
+	Response []byte
+}
+
 func init() {
 	gob.Register(map[string]string{})
 	gob.Register(Request{})
@@ -49,5 +59,9 @@ func init() {
 		SerializableStringConvRequest{})
 	gob.RegisterName("main.SerializableStringConvResponse",
 		SerializableStringConvResponse{})
+	gob.RegisterName("main.SerializableBinaryConvRequest",
+		SerializableBinaryConvRequest{})
+	gob.RegisterName("main.SerializableBinaryConvResponse",
+		SerializableBinaryConvResponse{})
 	gob.Register(utils.SerializableError{})
 }