First commands with basic structure.

- Moves DBManager to common.

watchtower-plugin/tower_info.py

@@ -0,0 +1,19 @@
+class TowerInfo:
+    def __init__(self, endpoint, available_slots):
+        self.endpoint = endpoint
+        self.available_slots = available_slots
+
+    @classmethod
+    def from_dict(cls, tower_data):
+        endpoint = tower_data.get("endpoint")
+        available_slots = tower_data.get("available_slots")
+
+        if any(v is None for v in [endpoint, available_slots]):
+            raise ValueError("Wrong appointment data, some fields are missing")
+        if available_slots is None:
+            raise ValueError("Wrong tower data, some fields are missing")
+
+        return cls(endpoint, available_slots)
+
+    def to_dict(self):
+        return self.__dict__