Add support for solo flights

autopilot/reservation.py

@@ -24,9 +24,17 @@ class Reservation(object):
             title = "Ground School"
         return title
 
+    @property
+    def lesson_suffix(self):
+        if self.instructor:
+            suffix = f"with {self.instructor}"
+        else:
+            suffix = "Solo"
+        return suffix
+
     @property
     def summary(self):
-        return f"{self.lesson_title} with {self.instructor}"
+        return f"{self.lesson_title} {self.lesson_suffix}"
 
     @property
     def description(self):