Add app_data file

src/sakia/data/entities/__init__.py

@@ -5,3 +5,4 @@ from .transaction import Transaction
 from .node import Node
 from .connection import Connection
 from .user_parameters import UserParameters
+from .app_data import AppData

src/sakia/data/entities/app_data.py

+import attr
+
+
+@attr.s()
+class AppData:
+    profiles = attr.ib(factory=list)

src/sakia/data/files/app_data.py

+import attr
+import json
+from ..entities import AppData
+
+
+@attr.s(frozen=True)
+class AppDataFile:
+    """
+    The repository for AppData
+    """
+    _file = attr.ib()
+
+    def save(self, app_data):
+        """
+        Commit a app_data to the database
+        :param sakia.data.entities.AppData app_data: the app_data to commit
+        """
+        with open(self._file, 'w') as outfile:
+            json.dump(attr.asdict(app_data), outfile, indent=4)
+
+    def load(self):
+        """
+        Update an existing app_data in the database
+        :param sakia.data.entities.AppData app_data: the app_data to update
+        """
+        with open(self._file, 'r') as json_data:
+            app_data = AppData(**json.load(json_data))
+        return app_data