pallet teerdays

[brenzi]

branded as TEERdays, but could be a sober "tokentime" just as well. The pallet is generic for all native tokens.

We're introducing a new non-transferrable token "TEERdays" which can be earned by bonding TEER
TEERdays shall serve as a governance token for L2 shards (i.e. Incognitee).
Multiplying bond with time makes governance more resilient against deep pocket attackers who suddenly decide to allocate a lot of TEER to take over governance. The time factor acts like inertia to governance.

This pallet is only the minimum necessary to start collecting TEERdays

notes:

• numeric stability:
  • 100years in milliseconds (Moment) are 42bits
  • 10MTEER with 12 digits are 60bits
  • 100years of total supply locked still fits u128
  • therefore, it is safe to use the Balance type for TEERdays

This PR also changes the toolchain to stable, except rustfmt

[clangenb]

Looks good to me, no unclarities.

But I do understand correctly that, so far, the Teerdays are not relevant elsewhere?

[brenzi]

thank you. You're right: TEERdays are consumed nowhere. The nomination pallet is left to do where TEERdays will be applied