Summary

RackReservation now exposes its required user field, backed by a minimal
User type (username only). Previously the wrapper had no way to set the user,
so rack reservations failed ingestion with Field user is required. Closes #75.

What changes

• Regenerated the ingester protobuf stubs (ingester_pb2.py / .pyi) and the
  ingester wrapper from the updated proto.
• RackReservation gains a user field; new minimal User wrapper (username).
• New example: docs/examples/rack_reservation.py (shows user=User(username=...)).

Usage

from netboxlabs.diode.sdk.ingester import Entity, RackReservation, User

Entity(rack_reservation=RackReservation(
    rack=...,
    units=[1, 2, 3],
    user=User(username="alice"),   # resolved against an existing NetBox user
))

The user is a reference to an existing NetBox user (matched by username); it is
not created by ingest.

Notes

• Generated code — regenerated from the updated ingester proto, not hand-edited.
• Depends on the corresponding ingester proto change.

Note: User is a match-only reference (resolved by username, never created via ingest), so there is no standalone user example — the correct usage is the nested User(...) shown in rack_reservation.