Contracts: Add an Internal Notice field

Current Notice field is not enough. Most organizations need two timings:

1. Notice, which is the official delay required by the supplier to renew the contract (by example 2 months);
2. Internal Delay, which is the time required by the organization to handle and prepare the renewal (hierarchy approval, validation process, etc.) (by example 3 weeks).

Currently, we have to merge both delays into the single Notice, but doing so 1) we lost the official delay, and 2) we have to round up delays (being unable to pick days but only months).

That's why I think adding a second Notice field (which could be name Internal Notice) would help to better manage contracts.