Bugfix/service request refactor size check (#553)

* refactor service requests from service header

* add APDU size checking and length feature

* add unit tests to check for length when passing NULL buffer

---------

Co-authored-by: Steve Karg <skarg@users.sourceforge.net>

src/bacnet/create_object.h

@@ -51,6 +51,9 @@ typedef uint32_t (*create_object_function)(uint32_t object_instance);
 extern "C" {
 #endif /* __cplusplus */
 
+BACNET_STACK_EXPORT
+size_t create_object_service_request_encode(
+    uint8_t *apdu, size_t apdu_size, BACNET_CREATE_OBJECT_DATA *data);
 BACNET_STACK_EXPORT
 int create_object_encode_service_request(
     uint8_t *apdu, BACNET_CREATE_OBJECT_DATA *data);