implemented the milestone

Author: nafiuishaaq

contract/src/lib.rs

@@ -313,6 +313,10 @@ pub struct Session {
     pub buyer: Address,
     pub seller: Address,
     pub amount: i128,
+    pub milestones: Vec<Milestone>,
+    pub rating: Rating,
+    pub started_at: u64,
+    pub deadline: Option<u64>,
     pub token_address: Option<Address>,
     pub status: SessionStatus,
     pub created_at: u64,