Add Inventory, borrowing system

[lislis]

We need a list of all the stuff in the space that can be borrowed.
Each item has

InventoryItem
----
Unique id
Name 
Better description in case two items are similar
Defects or damages

Then we need to track who currently borrowed an item

InventoryBorrows
----
who(User)
what(InventoryItem)
borrowed_when(Date)
returned_when(Date)
something_broke/ notes

And then we should be able to tell if the InventoryItem has a current borrow open, aka is borrowed. Plus we have a history of who borrowed what and so forth

[lislis]

Plus we should generate QR codes with the UUID that we can label on the real world items.
And a link to an endpoint where the borrow can happen, only for logged in users