Add support for tracking and payment of the registration fee

[florianschmidt1994]

The MVP in this case is to support generating tokens which can be used to check which participants payed for their team via different payment services. The most important method here it via bank transfer. The method of tracking payments with tokens should also be usable for the donations, if those should at some point run on our own payment system. The next steps are adding support for other payment methods, such as Paypal or CC. First POCs showed that Braintreepayment has a nice to use SDK which should allow an easy way of providing support for Paypal and CC

[florianschmidt1994]

One part of this is #67

[florianschmidt1994]

Idea for the process of paying the registration fee would be something along the lines

1. The participant (creator) creates a new team
2. An invoice will be added to the newly created team
3. Anywhere along this process can another participant (invitee) be invited to this team and join it
4. Any of these two participants can do a payment which will added to the invoice: The current rule for splitting the invoice is either 1x the full amount or 2x half of the amount. These rules should be implemented in a flexible way to allow the logic to be reused for further payment processes.
5. If the sum of all payments matches the invoice, the invoice and therefore the registration fee of the team will be marked as "payed"

Remark: I don't think we should add the amount of the registration fee as part of the source code and rather put it in the ignored config files. I also wouldn't disclose the concrete amount anywhere in the documentation or issues

Any opinions @Ardobras @thepiwo ?

[florianschmidt1994]

Payment should only be allowed when a team has the required two members

[thepiwo]

i like this idea

[florianschmidt1994]

I will remove this from milestone 1.0 as Braintree Payments are of the table now and therefore all payments will be added by administrators by hand.