Bootstrap copied BFF and local accounts with public Sendico contracts (#34)

backend/contracts/sendico/models/auth/session_identifier.yaml

@@ -0,0 +1,16 @@
+components:
+  schemas:
+    SessionIdentifier:
+      description: Identifies an authentication session by client and device.
+      type: object
+      additionalProperties: false
+      required:
+        - clientId
+        - deviceId
+      properties:
+        clientId:
+          description: Client application identifier associated with the session.
+          type: string
+        deviceId:
+          description: Device/server identifier associated with the client session.
+          type: string