* `authentik_host_rewrite_domains`: extra hostnames that reach the
authentik container but make it generate URLs (OIDC issuer, reset
links) as if requested from the canonical `authentik_domains[0]`.
Each entry gets its own traefik router and a URL-based loadbalancer
service that disables passHostHeader and pins X-Forwarded-Host via
middleware, so server-to-server calls on internal FQDNs keep traffic
in the LAN while the iss claim stays aligned with the public host.
Uses a network alias on the canonical FQDN so traefik (sharing the
network) resolves the URL upstream to this very container.
* proxy-app blueprint:
- `mode` (default `forward_single`) lets callers pick between proxy,
forward_single and forward_domain providers in one template.
- `allowed_groups`: when set, emit one PolicyBinding per group on
the application; authentik OR-evaluates bindings, so users in any
listed group pass and others are denied.
Existing inventories with an empty list see no behavioural change.