feat!: Added several fields to Quest struct

- Added field public
- Added optional field available_on
- Added optional field deadline
- Updated tests and CLI to use these fields

tests/main.rs

@@ -35,7 +35,10 @@ fn quest_one() {
         reward: 100,
         name: "Example easy quest".to_owned(),
         description: "Answer this quest without any attachments or comments".to_owned(),
-        answer: "Accept the answer if it has no attachments and an empty comment".to_owned()
+        answer: "Accept the answer if it has no attachments and an empty comment".to_owned(),
+        public: false,
+        available_on: None,
+        deadline: None
     };
 
     assert_eq!(*quest, expected);

tests/main/quests/1.toml

@@ -6,3 +6,4 @@ reward = 100
 name = "Example easy quest"
 description = "Answer this quest without any attachments or comments"
 answer = "Accept the answer if it has no attachments and an empty comment"
+public = false