Did not work :(
The error:
"{\"error\":{\"code\":\"0x0\",\"message\":\"An error occurred while validating input parameters: Microsoft.OData.ODataException: Does not support untyped value in non-open type.\\r\\n at System.Web.OData.Formatter.Deserialization.DeserializationHelpers.ApplyProperty(ODataProperty property, IEdmStructuredTypeReference resourceType, Object resource, ODataDeserializerProvider deserializerProvider, ODataDeserializerContext readContext)\\r\\n at System.Web.OData.Formatter.Deserialization.ODataResourceDeserializer.ApplyStructuralProperties(Object resource, ODataResourceWrapper resourceWrapper, IEdmStructuredTypeReference structuredType, ODataDeserializerContext readContext)\\r\\n at Microsoft.Crm.Extensibility.CrmODataEntityDeserializer.ApplyStructuralProperties(Object resource, ODataResourceWrapper resourceWrapper, IEdmStructuredTypeReference structuredType, ODataDeserializerContext readContext)\\r\\n at System.Web.OData.Formatter.Deserialization.ODataResourceDeserializer.ReadResource(ODataResourceWrapper resourceWrapper, IEdmStructuredTypeReference structuredType, ODataDeserializerContext readContext)\\r\\n at System.Web.OData.Formatter.ODataMediaTypeFormatter.ReadFromStream(Type type, Stream readStream, HttpContent content, IFormatterLogger formatterLogger)\",\"innererror\":{\"message\":\"An error occurred while validating input parameters: Microsoft.OData.ODataException: Does not support untyped value in non-open type.\\r\\n at System.Web.OData.Formatter.Deserialization.DeserializationHelpers.ApplyProperty(ODataProperty property, IEdmStructuredTypeReference resourceType, Object resource, ODataDeserializerProvider deserializerProvider, ODataDeserializerContext readContext)\\r\\n at System.Web.OData.Formatter.Deserialization.ODataResourceDeserializer.ApplyStructuralProperties(Object resource, ODataResourceWrapper resourceWrapper, IEdmStructuredTypeReference structuredType, ODataDeserializerContext readContext)\\r\\n at Microsoft.Crm.Extensibility.CrmODataEntityDeserializer.ApplyStructuralProperties(Object resource, ODataResourceWrapper resourceWrapper, IEdmStructuredTypeReference structuredType, ODataDeserializerContext readContext)\\r\\n at System.Web.OData.Formatter.Deserialization.ODataResourceDeserializer.ReadResource(ODataResourceWrapper resourceWrapper, IEdmStructuredTypeReference structuredType, ODataDeserializerContext readContext)\\r\\n at System.Web.OData.Formatter.ODataMediaTypeFormatter.ReadFromStream(Type type, Stream readStream, HttpContent content, IFormatterLogger formatterLogger)\",\"type\":\"Microsoft.Crm.CrmHttpException\",\"stacktrace\":\" at Microsoft.Crm.Extensibility.OData.CrmODataUtilities.ValidateInputParameters(ModelStateDictionary controllerModelState)\\r\\n at Microsoft.Crm.Extensibility.OData.EntityController.PostEntitySetImplementation(String& entitySetName, EdmEntityObject entityObject)\\r\\n at Microsoft.Crm.Extensibility.OData.CrmODataUtilities.<>c__DisplayClass10_0`2.<InvokeActionAndLogMetric>b__0()\\r\\n at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute[TResult](ILogger logger, EventId eventId, ActivityType activityType, Func`1 func, IEnumerable`1 additionalCustomProperties)\\r\\n at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute[TResult](ILogger logger, XrmTelemetryActivityType activityType, Func`1 func)\\r\\n at lambda_method(Closure , Object , Object[] )\\r\\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass10.<GetExecutor>b__9(Object instance, Object[] methodParameters)\\r\\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)\\r\\n--- End of stack trace from previous location where exception was thrown ---\\r\\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()\\r\\n--- End of stack trace from previous location where exception was thrown ---\\r\\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()\\r\\n--- End of stack trace from previous location where exception was thrown ---\\r\\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()\"}}}"