Refundable Subscription Mechanism

[SaberDoTcodeR]

This PSP is related to our implementation of the SubsCrypt Project. This standard can be used in any token contract that supports built-in subscription methods.

[lamafab]

Hi @SaberDoTcodeR, thanks for the PR.

• It might be useful to specify the exact types of the parameters (reference).
• There should probably be a more enhanced description about the concept of a "provider": in the Auth section you mentioned a "token" that should be used when hashing the password. I assume this is related to a identifier of a provider?
• In the table, it would be convenient to indicate which function is used by the user and which one is used by the provider.