## Why
All Authentik OIDC logins (ArgoCD, Grafana, Rancher, LiteLLM, NetBox) fail
with `invalid_request` / "The request is otherwise malformed". Authentik
2026.5 added an explicit `grant_types` allow-list to the OAuth2 provider
(model default = empty list). Our module never set it, so every provider has
`grant_types = []`, and `authorize.py` rejects the authorization_code grant
(`if self.grant_type not in self.provider.grant_types`) before any user auth.
## Change
- modules/authentik: add a `grant_types` field to the `providers_oauth2`
variable, defaulting to `["authorization_code", "refresh_token"]` (the
standard confidential web-app set), and wire it into
`authentik_provider_oauth2`.
## Plan
`0 to add, 5 to change, 0 to destroy` — each existing oauth2 provider's
`grant_types` goes `[] -> ["authorization_code", "refresh_token"]`; no other
attributes change. Baseline plan (pre-change) was clean (no netbox/state drift).
Claude-Session: https://claude.ai/code/session_015ur3i7D2azsMAWTSVABApv
unkinben