[CSAPI]: Preserve exception cause on invalid payload

For some exceptions, the cause backtrace provides necessary details for
debugging the actual cause of the issue, since the message is not always
detailed enough.

sensorhub-service-consys/src/main/java/org/sensorhub/impl/service/consys/resource/BaseResourceHandler.java

@@ -355,7 +355,7 @@ protected void create(final RequestContext ctx) throws IOException
         }
         catch (ResourceParseException e)
         {
-            throw ServiceErrors.invalidPayload("Invalid payload: " + e.getMessage());
+            throw ServiceErrors.invalidPayload("Invalid payload: " + e.getMessage(), e);
         }
     }
 
@@ -399,7 +399,7 @@ protected void update(final RequestContext ctx, final String id) throws IOExcept
         }
         catch (ResourceParseException e)
         {
-            throw ServiceErrors.invalidPayload("Invalid payload: " + e.getMessage());
+            throw ServiceErrors.invalidPayload("Invalid payload: " + e.getMessage(), e);
         }
 
         // update in datastore

sensorhub-service-sweapi/src/main/java/org/sensorhub/impl/service/sweapi/ServiceErrors.java

@@ -42,7 +42,13 @@ public static InvalidRequestException badRequest(String msg)
 
     public static InvalidRequestException invalidPayload(String msg)
     {
-        return new InvalidRequestException(ErrorCode.BAD_PAYLOAD, msg);
+        return invalidPayload(msg, null);
+    }
+
+
+    public static InvalidRequestException invalidPayload(String msg, Throwable cause)
+    {
+        return new InvalidRequestException(ErrorCode.BAD_PAYLOAD, msg, cause);
     }