Add service fee log (#423)

This PR adds a log for the service fee charged to solvers in the COW DAO
bonding pool.

This log is useful since it determines the budget for ongoing bounties.

This PR does not change the behavior of the code and no additional test
was added.

---------

Co-authored-by: Haris Angelidakis <[email protected]>

src/fetch/payouts.py

@@ -138,6 +138,14 @@ def reward_scaling(self) -> Fraction:
         The reward is multiplied by this factor"""
         return 1 - SERVICE_FEE_FACTOR * self.service_fee
 
+    def total_service_fee(self) -> Fraction:
+        """Total service fee charged from rewards"""
+        return (
+            SERVICE_FEE_FACTOR
+            * self.service_fee
+            * (self.primary_reward_cow + self.quote_reward_cow)
+        )
+
     def is_overdraft(self) -> bool:
         """
         True if the solver's complete combined data results in a net negative
@@ -529,13 +537,19 @@ def construct_payouts(
     performance_reward = complete_payout_df["primary_reward_cow"].sum()
     quote_reward = complete_payout_df["quote_reward_cow"].sum()
 
+    service_fee = sum(
+        RewardAndPenaltyDatum.from_series(payment).total_service_fee()
+        for _, payment in complete_payout_df.iterrows()
+    )
+
     dune.log_saver.print(
         "Payment breakdown (ignoring service fees):\n"
         f"Performance Reward: {performance_reward / 10 ** 18:.4f}\n"
         f"Quote Reward: {quote_reward / 10 ** 18:.4f}\n"
         f"Protocol Fees: {final_protocol_fee_wei / 10 ** 18:.4f}\n"
         f"Partner Fees Tax: {partner_fee_tax_wei / 10 ** 18:.4f}\n"
-        f"Partner Fees: {total_partner_fee_wei_taxed / 10 ** 18:.4f}\n",
+        f"Partner Fees: {total_partner_fee_wei_taxed / 10 ** 18:.4f}\n"
+        f"COW DAO Service Fees: {service_fee / 10 ** 18:.4f}\n",
         category=Category.TOTALS,
     )
     payouts = prepare_transfers(