Make Jitsi links not appear for unassigned requests

What does this mr do?

Makes the Jitsi link appear on the request overview only if the person requesting it is the TA assigned to the request.

Actions taken to fix bug

Create a method which checks whether the lab is an online lab and whether the assigned TA (if any) is the one with the id passed as a parameter.

Does this MR meet the acceptance criteria?

• I have added a changelog entry to reflect the significant changes I made and the bug I fixed.
• A test was created to test the bug.
• I have updated the documentation accordingly.
• I adhere to the style guide.

src/main/java/nl/tudelft/ewi/queue/model/Request.java

@@ -237,6 +237,18 @@ public class Request implements RecordsEvents<Request>, Serializable, Comparable
 		this.jitsiRoom = jitsiRoom;
 	}
 
+	/**
+	 * Determines whether the Jitsi Room should be displayed for a user.
+	 *
+	 * @param  user the user
+	 * @return      true if the Jitsi room should be displayed
+	 */
+	public boolean shouldDisplayJitsiRoom(User user) {
+		return lab.isOnline() && ((assistant != null && assistant.equals(user))
+				|| user.isAdmin()
+				|| (user.isTeacher() && !user.teaches(getLab().getCourse())));
+	}
+
 	public Lab getLab() {
 		return lab;
 	}