Add event_id and guest_id fields to RSVPSchemaBase

This update introduces event_id and guest_id fields to the RSVPSchemaBase model, ensuring better tracking of RSVP details. These additions enhance data association and model usability.

backend/app/schemas/rsvp.py

@@ -12,6 +12,8 @@ class RSVPStatus(str, Enum):
 
 
 class RSVPSchemaBase(BaseModel):
+    event_id: UUID
+    guest_id: UUID
     status: RSVPStatus = Field(...)
     number_of_guests: int = Field(default=1, ge=1)
     response_message: str | None = None