feat(config): add tokenUrl, clientId, clientSecret to auth config (#17)

Closes homelab#12 (P3.7)

## Changes

- `AuthConfig`: added `TokenURL`, `ClientID`, `ClientSecret` fields
- `loader.go`: reads `tokenUrl`/`clientId` from YAML, `ClientSecret` from `AUTH_CLIENT_SECRET` env
- `deployment.yaml`: `AUTH_CLIENT_SECRET` from `api-gw-client-secret` Secret (optional)
- `gateway-config-secret.enc.yaml` + `configmap.yaml`: added `tokenUrl` and `clientId`

## Secret never in YAML

`clientSecret` deliberately omitted from YAML struct. Loaded from env only.

## Tests

3 tests: full config load, env-only secret, backward compat (missing fields = zero).

Co-authored-by: poimen <[email protected]>

internal/config/auth_config_test.go

@@ -0,0 +1,104 @@
+package config_test
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"forgejo.riotpiao.com/rock/homelab-frontend/internal/config"
+)
+
+func TestLoadAuthConfig_TokenURLAndClientID(t *testing.T) {
+	yaml := `
+routes: []
+models: []
+auth:
+  enabled: true
+  issuer: "https://authentik.example.com/application/o/api-gw/"
+  audience: "api-gw"
+  jwksUrl: "https://authentik.example.com/application/o/api-gw/jwks/"
+  requiredCapability: "llm:inference"
+  tokenUrl: "https://authentik.example.com/application/o/token/"
+  clientId: "api-gw"
+`
+	dir := t.TempDir()
+	path := filepath.Join(dir, "config.yaml")
+	if err := os.WriteFile(path, []byte(yaml), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	// Set env for client secret
+	t.Setenv("AUTH_CLIENT_SECRET", "test-secret-value")
+
+	_, _, _, auth, err := config.LoadRoutesAndModelsFromFile(path)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if !auth.Enabled {
+		t.Error("auth should be enabled")
+	}
+	if auth.TokenURL != "https://authentik.example.com/application/o/token/" {
+		t.Errorf("tokenUrl = %q, want authentik token endpoint", auth.TokenURL)
+	}
+	if auth.ClientID != "api-gw" {
+		t.Errorf("clientId = %q, want api-gw", auth.ClientID)
+	}
+	if auth.ClientSecret != "test-secret-value" {
+		t.Errorf("clientSecret = %q, want test-secret-value", auth.ClientSecret)
+	}
+}
+
+func TestLoadAuthConfig_ClientSecretFromEnvOnly(t *testing.T) {
+	yaml := `
+routes: []
+models: []
+auth:
+  enabled: true
+  tokenUrl: "https://example.com/token/"
+  clientId: "test"
+`
+	dir := t.TempDir()
+	path := filepath.Join(dir, "config.yaml")
+	os.WriteFile(path, []byte(yaml), 0644)
+
+	// No AUTH_CLIENT_SECRET env set
+	t.Setenv("AUTH_CLIENT_SECRET", "")
+
+	_, _, _, auth, err := config.LoadRoutesAndModelsFromFile(path)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if auth.ClientSecret != "" {
+		t.Errorf("clientSecret should be empty when env not set, got %q", auth.ClientSecret)
+	}
+}
+
+func TestLoadAuthConfig_BackwardCompatible(t *testing.T) {
+	// Config without tokenUrl/clientId should still load (zero values)
+	yaml := `
+routes: []
+models: []
+auth:
+  enabled: true
+  issuer: "https://example.com/"
+  jwksUrl: "https://example.com/jwks/"
+  requiredCapability: "llm:inference"
+`
+	dir := t.TempDir()
+	path := filepath.Join(dir, "config.yaml")
+	os.WriteFile(path, []byte(yaml), 0644)
+
+	_, _, _, auth, err := config.LoadRoutesAndModelsFromFile(path)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if auth.TokenURL != "" {
+		t.Errorf("tokenUrl should be empty, got %q", auth.TokenURL)
+	}
+	if auth.ClientID != "" {
+		t.Errorf("clientId should be empty, got %q", auth.ClientID)
+	}
+}

internal/config/config.go

@@ -50,6 +50,12 @@ type AuthConfig struct {
 	JWKSURL string
 	// RequiredCapability is the permission required for LLM inference (e.g., "llm:inference").
 	RequiredCapability string
+	// TokenURL is the Authentik token endpoint for password/refresh grants.
+	TokenURL string
+	// ClientID is the OAuth2 client ID for token exchange.
+	ClientID string
+	// ClientSecret is the OAuth2 client secret (loaded from env, never from config file).
+	ClientSecret string
 }
 
 // Route represents a single route and its upstream configuration.

internal/config/loader.go

@@ -25,6 +25,8 @@ type rawAuth struct {
 	Audience           string `yaml:"audience"`
 	JWKSURL            string `yaml:"jwksUrl"`
 	RequiredCapability string `yaml:"requiredCapability"`
+	TokenURL           string `yaml:"tokenUrl"`
+	ClientID           string `yaml:"clientId"`
 }
 
 // rawRoute represents a single route in the YAML configuration.
@@ -176,6 +178,9 @@ func LoadRoutesAndModelsFromFile(path string) (map[string]*Route, map[string]*Mo
 		Audience:           raw.Auth.Audience,
 		JWKSURL:            raw.Auth.JWKSURL,
 		RequiredCapability: raw.Auth.RequiredCapability,
+		TokenURL:           raw.Auth.TokenURL,
+		ClientID:           raw.Auth.ClientID,
+		ClientSecret:       os.Getenv("AUTH_CLIENT_SECRET"),
 	}
 
 	return routes, models, adapters, authConfig, nil