I have been mandated to create TASKS in a JIRA project via XMLHTTP POST request.
I have overcome, connectivity and authorization.
But I keep getting baffled with errors that keep coming when I try to send values from drop-down list.
I have queried my JIRA project in order to get the list of fields, their type, ID, etc... (see attached fields.png)

No matter what I try, I always get errors for single-select customfield.
If I assigned the value like this:
{"value","13716"}
I get this error:
Field with id 'customfield_12120' named 'Department' has these errors : Option id 'null' is not valid"
in what was returned to me by JIRA upon my request for fields, I do not see an ID for tany of the validValues. I have searched for that error but what I found wasn't conclusive so I tried this:
{"id":"12120","value":"13716"}
or
{"id":"0","value":"13716"}
I get this error:
Please provide a valid value for field 'Department'
Now if you look at the image above, you will see that the value 13716 is a valid value.
I am lost...anyone got an idea?