feat: Add StrategySelector

This way the user could be able to extend this easily

src/encoding/strategy_selector.rs

@@ -0,0 +1,23 @@
+use crate::encoding::models::Order;
+use crate::encoding::strategy_encoder::{
+    SequentialExactInStrategyEncoder, SingleSwapStrategyEncoder, SlipSwapStrategyEncoder,
+    StrategyEncoder,
+};
+
+pub trait StrategySelector {
+    fn select_strategy(&self, order: &Order) -> Box<dyn StrategyEncoder>;
+}
+
+pub struct DefaultStrategySelector;
+
+impl StrategySelector for DefaultStrategySelector {
+    fn select_strategy(&self, order: &Order) -> Box<dyn StrategyEncoder> {
+        if order.swaps.len() == 1 {
+            Box::new(SingleSwapStrategyEncoder {})
+        } else if order.swaps.iter().all(|s| s.split == 0.0) {
+            Box::new(SequentialExactInStrategyEncoder {})
+        } else {
+            Box::new(SlipSwapStrategyEncoder {})
+        }
+    }
+}