Duniter quota pallet

Duniter identity system allows to allocate quota and refund transaction fees when not consumed.

General behavior

Quota system is plugged to transactions fees which is a rather critical aspect of substrate. That's why in duniter-account pallet OnChargeTransaction implementation, the default behavior is preserved, and refunds are added to a queue handeled in on_idle.

Path for a refund

This is what happens on a transaction:

• frame-executive calls OnChargeTransaction implementations
• duniter-account OnChargeTransaction implementation is called, and if an identity is linked to the account who pays the fees, request_refund is called
• request_refund implementation of quota pallet determines whether the fees are eligible for refund based on the identity and then call queue_refund
• queue_refund adds a refund to the RefundQueue which will be processed in on_idle
• during on_idle, quota pallet processes the refund queue within the supplied weight limit with process_refund_queue
• for each refund in the RefundQueue, try_refund is called
• it first tries to use quotas to refund fees with spend_quota
• if a certain amount of quotas has been spend, it actually performs the refund with do_refund, taking currency from the RefundAccount to give it back to the account who paid the fee

The conditions for a refund to happen are:

1. an identity is linked to the account who pays the fees
2. some quotas are defined for the identity and have a non-null value after update

TODO

• sanity test checking that only member identities have quota