issues with encoding post_data with maxurl

Hello,

I'm currently having issues encoding post_data when using maxurl.

I need to send an object (using dict) that looks like this:

{
userId: '61d3297690e19cc4d1245182',
position: { x: 26.146447430333367, y: -1.1071898829533802 },
label: 'label',
dataType: 'String'
}

The documentation for maxurl seems to imply that I can just send a dictionary as post_data and it will encode properly, but unfortunately it seems to send a malformed object. This is what shows up in my server:
{
'{\r\n\t"userId" : "61d3297690e19cc4d1245182",\r\n\t"position" : \t{\r\n\t\t"x" : 26.146447430333367,\r\n\t\t"y" : -1.10718988295338\r\n\t}\r\n,\r\n\t"label" : "label",\r\n\t"dataType" : "String"\r\n}\r\n': ''
}

I can't seem to get maxurl post_data to handle anything other than URL encoded strings. I've managed to form a string from a dict, but there are too many edge cases to make that feel feasible.

Can someone help me figure out how to do this properly?

Here is a small example patch: