Encodes RewardsCoordinator.processClaim(claim, recipient). Rewards are sent to the staker address.
Merkle roots are posted weekly (Tuesdays) with a 7-day activation delay before they are claimable.

Nonce handling: The nonce is computed at call time. If you prepare multiple transactions before broadcasting, they will share the same nonce and only the first will succeed. Broadcast and confirm each transaction before preparing the next.