moved definitions of data classes into module where used

shared/mongodb/classes/contact.py

@@ -0,0 +1,12 @@
+"""Definition of ContactData data model."""
+
+from __future__ import annotations
+
+from .data_model import DataModel
+
+
+class ContactData(DataModel):
+    """ContactData data model."""
+
+    offer: float
+    demand: float