Adapt SubscriptionManager agent to changes in contract

In particular, new "size" parameter and different Policy struct layout

nucypher/blockchain/eth/agents.py

@@ -956,7 +956,7 @@ class SubscriptionManagerAgent(EthereumContractAgent):
 
     @contract_api(CONTRACT_CALL)
     def rate_per_second(self) -> Wei:
-        result = self.contract.functions.RATE_PER_SECOND().call()
+        result = self.contract.functions.feeRate().call()
         return Wei(result)
 
     @contract_api(CONTRACT_CALL)
@@ -969,10 +969,11 @@ class SubscriptionManagerAgent(EthereumContractAgent):
         record = self.contract.functions.policies(policy_id).call()
         policy_info = self.PolicyInfo(
             sponsor=record[0],
+            start_timestamp=record[1],
+            end_timestamp=record[2],
+            size=record[3],
             # If the policyOwner addr is null, we return the sponsor addr instead of the owner.
-            owner=record[0] if record[1] == NULL_ADDRESS else record[1],
-            start_timestamp=record[2],
-            end_timestamp=record[3]
+            owner=record[0] if record[4] == NULL_ADDRESS else record[4]
         )
         return policy_info
 
@@ -984,6 +985,7 @@ class SubscriptionManagerAgent(EthereumContractAgent):
     def create_policy(self,
                       policy_id: bytes,
                       transacting_power: TransactingPower,
+                      size: int,
                       start_timestamp: Timestamp,
                       end_timestamp: Timestamp,
                       value: Wei,
@@ -993,6 +995,7 @@ class SubscriptionManagerAgent(EthereumContractAgent):
         contract_function: ContractFunction = self.contract.functions.createPolicy(
             policy_id,
             owner_address,
+            size,
             start_timestamp,
             end_timestamp
         )

nucypher/policy/payment.py

@@ -161,6 +161,7 @@ class SubscriptionManagerPayment(ContractPayment):
         receipt = self.agent.create_policy(
             value=policy.value,                   # wei
             policy_id=bytes(policy.hrac),         # bytes16 _policyID
+            size=len(policy.kfrags),              # uint16
             start_timestamp=policy.commencement,  # uint16
             end_timestamp=policy.expiration,      # uint16
             transacting_power=policy.publisher.transacting_power