@roma.taju you have a pretty complex body, so if I will be in your shoes I will use a different approach.
E.g I will store the body template as a file, and do the needed substitutions from a testcase, using the groovy SimpleTemplate engine.
see: Template engines
I made an example of how this can be achieved some time ago, here:
So I suggest to you to build the entire body in a testcase and pass it to the testobject as a single string variable.