feat: Add propeller swap encoders

- Add setup for package
- Add docs
- Add balancer implementation and test
- Add CI:
  - Add setup action
  - Add test and format CI
- Add CD: Publish python package to AWS

propeller-swap-encoders/propeller_swap_encoders/balancer.py

@@ -0,0 +1,33 @@
+from typing import Any
+
+from core.encoding.interface import SwapStructEncoder
+from core.type_aliases import Address
+from eth_abi.packed import encode_abi_packed
+from hexbytes import HexBytes
+
+
+class BalancerSwapStructEncoder(SwapStructEncoder):
+    def encode_swap_struct(
+        self, swap: dict[str, Any], receiver: Address, exact_out: bool, **kwargs
+    ) -> bytes:
+        """
+        Parameters:
+        ----------
+        swap
+            The swap to encode
+        receiver
+            The receiver of the buy token
+        exact_out
+            Whether the amount encoded is the exact amount out
+        """
+        return encode_abi_packed(
+            ["address", "address", "bytes32", "address", "bool", "bool"],
+            [
+                swap["sell_token"].address,
+                swap["buy_token"].address,
+                HexBytes(swap["pool_id"]),
+                receiver,
+                exact_out,
+                swap["token_approval_needed"],
+            ],
+        )