refactor: extract models (#2759)

lnbits/core/models/webpush.py

@@ -0,0 +1,15 @@
+from datetime import datetime
+
+from pydantic import BaseModel
+
+
+class CreateWebPushSubscription(BaseModel):
+    subscription: str
+
+
+class WebPushSubscription(BaseModel):
+    endpoint: str
+    user: str
+    data: str
+    host: str
+    timestamp: datetime