Barter stand to automatically check configuration

[Fostik]

Currently barter stands doesn't provide any feedback on whether configuration of items on sale is right.
There are few possible cases and combinations when barter stand will display items and display them on table, although once you attempt to buy - it will display you error that stand couldn't take price.
Currently on most popular community market there are vast amount of stands and close to thousand of items being sold, some percentage of traded items configured wrong and can't be bought, although you will only know that once you attempt to buy having required price with you.

It would be really good to have automatic healthcheck performed by barter stand. Once you open barter stand and server returns you a result to your client to render window, healtheck that is attempting to buy items must happen, i.e. barter stand performs dry buy without buying item, and returns status of the operation. Result of healthcheck should affect the items displayed, filtering off or marking items that can't be bought.

This will address quite significant marketing QoL issue, such as:
- Traders setting their stuff for sale on markets sometimes making mistakes, and some market positions can't be sold without them knowing. To be 100% sure you can only check yourself by buying something.
- Customers of markets might expect to buy some good, although up to the moment they bring required item barter will display them error.