EgressRoute now extends egress_addon_core.Route, which holds the four
wire-visible fields (host, path_allowlist, auth_scheme, token_env).
EgressRoute adds only the three host-side fields (token_ref, roles,
tls_passthrough) that are never serialised to the sidecar.
_route_to_yaml_fields is typed as Route -> dict, making the host→wire
boundary explicit: only fields declared on the base class cross into the
YAML the addon reads.
didericis-claude
07c8593999