IGetUserListings Returns classified listings for a given user
format - The response format. Default: json
callback - JSONP only. Used for the function call.
key - Your backpack.tf API key.
appid - The AppID to retrieve listings for. Default: 440 (Team Fortress 2)
steamid - The SteamID to retrieve listings for.
success - 1 if successful, 0 otherwise.
message - if success is 0, this contains the reason for failure.
current_time - The server time when the response was created.
listings - an array of classified listings.
currencies - an array of currencies used to price the listing.
The keys are the internal names of currencies that can be identified using the IGetCurrencies API.
The values are the quantity of currencies that were set on the Create Listing page.
item - the item in the listing.
The information displayed here is more or less the same as what you'd get out of the official GetItems
In some cases, there may be differences for items that we need to gather information from the
Community API for.
In which case, some additional keys may exist to help you identify the item.
details - the message on the listing.
bump - a UNIX timestamp of when the listing was last bumped.
created - a UNIX timestamp of when the listing was created.
id - the listing's internal ID. This only usually shows up in listing HTML.
intent - the intent of the listing (1 if Selling, 0 if Buying).