Strategy and Vault Interfaces

What You Are Building

Two interfaces in one file: IStrategy (what the vault calls on a strategy) and IVaultAPI (what a strategy calls on its vault). No contracts, no inheritance chain, section 7 is purely the boundary between two separate inheritance lines.

Compound did the same thing in section 9 with ComptrollerInterface declared up front so the Comptroller and CToken sides could be developed independently. Interface design is a discipline. Get it right here and the rest of Part 2 falls into place.