Prefer refering to external contracts by their interface over their implementation

[marcoatpaladin]

gif-next/contracts/registry/Registry.sol

Line 63 in 065e0af

ReleaseRegistry public _releaseRegistry;

Throughout the codebase, the actual implementation type is often used to type external contracts. It's cleaner to use the interface type instead. This more clearly documents that its actually that "interface" which is being used and needed here, as the contract in question is allowed to differ from the specific contract version you compiled with.

This is informational as this is syntax sugar, and does not affect anything at the lower level.