fix time.Time fields not being saved

via adding a special case in the `serializeIDs` function (in document_internals.go)

document_internals.go

@@ -83,10 +83,14 @@ func serializeIDs(input interface{}) interface{} {
 						}
 					}
 
+				} else {
+					if fv.Type() == reflect.TypeFor[time.Time]() {
+						ret0[bbson.Name] = fv.Interface()
 					} else {
 						ret0[bbson.Name] = serializeIDs(fv.Interface())
 					}
 				}
+			}
 
 			ret = ret0
 		}