Assign and compute royalties on items

[jessevondoom]

We need a mechanism to assign specific royalty splits on a per-item basis. The end goal is for us to be able to split out payments to any/all parties who are owed from the sale of a tract/release/file. Every item needs a unique royalty formula that we'll generate in a wizard-style interface. A few things to think about:

• We'll need breakpoints based on date or money. So if an item has earned $5000 it might compute at one rate but after it hits $7500 that rate might change. We might also set a breakpoint based on date — sales before March 1 compute with one rate and another after. (I'd think offering breakpoint of either type in a wizard interface would be enough.)
• We need to consider multiple parties. It's not just one or two...could be many rights-holders.
• In the case of a release, we'll need to take into account that not every track has the same splits. We can safely stick to one breakpoint, but we'll need to ask users if royalties should be calculated for the release as a whole, or if we'll need a more complex calculator — something that steps through each track and ultimately computes a more complex rate for the release. (Think of one song on a 10 track album as 10% of the total rights. So if one rights-holder has 40% of that one track they'll be assigned 4% of the overall rate for the release.)
• Ultimately we'll need to be able to export this data. (A separate issue.) So if the wizard can generate human-readable notes that would be ideal. Explaining that one rights-holder is getting 4% of the overall because of a 40% stake in one track out of ten is HUGELY helpful a year after you've set the rate.
• Rights should be able to be assigned to a user in the system (people/id) or simply as a name/string. Longer term we might want to explore automating pay-outs so having the ability to link to other user accounts is a big deal.

[jessevondoom]

All unassigned percentages on an item should be considered owned/kept by the user.

[christopherleckie]

Ability to get a payout prompt via email or main page notification would be really good here