purchase UOM by supplier
Currently there is a default UOM by product
and a single purchase UOM for all suppliers.
Having a *default* purchase UOM is okay, but we need supplier specific
purchase UOM for overide as they may not use the same base.
For example: for bars 5m of copper Tubing
we have suppliers whose price is by the bar (5m) others by meter.
Naturally, for physical stock, we have the bars with the default UOM == 5m
For sale UOM (actually for project estimations) this is always by meter.
This is preventing us from merging these products with different suppliers.