Creates ExtendedAppointment as an appointment with user information

teos/extended_appointment.py

@@ -0,0 +1,37 @@
+from common.appointment import Appointment
+
+
+class ExtendedAppointment(Appointment):
+    def __init__(self, locator, to_self_delay, encrypted_blob, user_id):
+        super().__init__(locator, to_self_delay, encrypted_blob)
+        self.user_id = user_id
+
+    @classmethod
+    def from_dict(cls, appointment_data):
+        """
+        Builds an appointment from a dictionary.
+
+        This method is useful to load data from a database.
+
+        Args:
+            appointment_data (:obj:`dict`): a dictionary containing the following keys:
+                ``{locator, to_self_delay, encrypted_blob, expiry}``
+
+        Returns:
+            :obj:`ExtendedAppointment <teos.extended_appointment.ExtendedAppointment>`: An appointment initialized
+            using the provided data.
+
+        Raises:
+            ValueError: If one of the mandatory keys is missing in ``appointment_data``.
+        """
+
+        appointment = Appointment.from_dict(appointment_data)
+        user_id = appointment_data.get("user_id")
+
+        if not user_id:
+            raise ValueError("Wrong appointment data, user_id is missing")
+
+        else:
+            appointment = cls(appointment.locator, appointment.to_self_delay, appointment.encrypted_blob, user_id)
+
+        return appointment