feat(substreams): add substreams for Uniswap v2 and v3

substreams/ethereum-uniswap-v2/src/store_key.rs

@@ -0,0 +1,16 @@
+#[derive(Clone)]
+pub enum StoreKey {
+    Pool,
+}
+
+impl StoreKey {
+    pub fn get_unique_pool_key(&self, key: &str) -> String {
+        format!("{}:{}", self.unique_id(), key)
+    }
+
+    pub fn unique_id(&self) -> String {
+        match self {
+            StoreKey::Pool => "Pool".to_string(),
+        }
+    }
+}