Add mjs_detachBody to C API.

PiperOrigin-RevId: 626947850
Change-Id: I7c897048098ecd4f2247725ef2d378dbd00ef4a0

src/user/user_api.cc

@@ -110,6 +110,16 @@ const char* mjs_getError(mjSpec* s) {
 
 
 
+// Detach body from mjSpec, return 0 if success.
+int mjs_detachBody(mjSpec* s, const mjsBody* b) {
+  mjCModel* model = static_cast<mjCModel*>(s->element);
+  mjCBody* body = static_cast<mjCBody*>(b->element);
+  *model -= *body;
+  return 0;
+}
+
+
+
 // check if model has warnings
 int mjs_isWarning(mjSpec* s) {
   mjCModel* modelC = static_cast<mjCModel*>(s->element);
@@ -126,6 +136,14 @@ void mjs_deleteSpec(mjSpec* s) {
 
 
 
+// delete body
+void mjs_deleteBody(mjsBody* b) {
+  mjCBody* body = static_cast<mjCBody*>(b->element);
+  delete body;
+}
+
+
+
 // add child body to body, return child spec
 mjsBody* mjs_addBody(mjsBody* bodyspec, mjsDefault* defspec) {
   mjCDef* def = defspec ? static_cast<mjCDef*>(defspec->element) : 0;