feat: add course information

ApiDto/Responses/GroupDetailsResponse.cs

@@ -15,6 +15,11 @@ public class GroupDetailsResponse
     /// </summary>
     public required string Name { get; set; }
 
+    /// <summary>
+    /// Gets or sets the course number of the group.
+    /// </summary>
+    public int CourseNumber { get; set; }
+
     /// <summary>
     /// Gets or sets the unique identifier of the faculty to which the group belongs (optional).
     /// </summary>