feat: Separate encoding swaps from encoding txs

This way the user is responsible for encoding the Tycho Router method inputs that are used as guardrails in execution.

Interface changes:
- Create EncodedSolution
- StrategyEncoder
  - don't need to know have permit2 or token_in_already_in_router as attributes anymore
  - encode_strategy returns EncodedSolution now (no method encoding done here now)
- TychoEncoder
  - add encode_solution() method. This is the recommended method for users
  - needs to have permit2, token_in_already_in_router and router_address as attributes
  - permit creation is made in the router now

Also:
- create encoding_utils.rs
- update all tests

Took 2 hours 42 minutes


Took 3 minutes

Took 13 minutes

src/encoding/models.rs

@@ -1,3 +1,4 @@
+use alloy_primitives::PrimitiveSignature as Signature;
 use hex;
 use num_bigint::BigUint;
 use serde::{Deserialize, Serialize};
@@ -8,6 +9,7 @@ use tycho_common::{
 
 use crate::encoding::{
     errors::EncodingError,
+    evm::approvals::permit2::PermitSingle,
     serde_primitives::{biguint_string, biguint_string_option},
 };
 
@@ -96,6 +98,22 @@ pub struct Transaction {
     pub data: Vec<u8>,
 }
 
+/// Represents a solution that has been encoded for execution.
+///
+/// # Fields
+/// * `swaps`: Encoded swaps to be executed.
+/// * `selector`: The selector of the function to be called.
+/// * `n_tokens`: Number of tokens in the swap.
+/// * `permit`: Optional permit for the swap (if permit2 is enabled).
+/// * `signature`: Optional signature for the swap (if permit2 is enabled).
+pub struct EncodedSolution {
+    pub swaps: Vec<u8>,
+    pub selector: String,
+    pub n_tokens: usize,
+    pub permit: Option<PermitSingle>,
+    pub signature: Option<Signature>,
+}
+
 /// Represents necessary attributes for encoding an order.
 ///
 /// # Fields