feat(authentik): add AuthentikUser and AuthentikConfig types

Introduce core types for the Authentik forward-auth integration:
- AuthentikConfig with Issuer, ClientID, TrustedProxy, PublicPaths
- AuthentikUser with Username, Email, Name, UID, Groups, Entitlements, JWT
- HasGroup helper for group membership checks

Co-Authored-By: Virgil <virgil@lethean.io>

authentik.go

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: EUPL-1.2
+
+package api
+
+// AuthentikConfig holds settings for the Authentik forward-auth integration.
+type AuthentikConfig struct {
+	// Issuer is the OIDC issuer URL (e.g. https://auth.example.com/application/o/my-app/).
+	Issuer string
+
+	// ClientID is the OAuth2 client identifier.
+	ClientID string
+
+	// TrustedProxy enables reading X-authentik-* headers set by a reverse proxy.
+	// When false, headers are ignored to prevent spoofing from untrusted sources.
+	TrustedProxy bool
+
+	// PublicPaths lists additional paths that do not require authentication.
+	// /health and /swagger are always public.
+	PublicPaths []string
+}
+
+// AuthentikUser represents an authenticated user extracted from Authentik
+// forward-auth headers or a validated JWT.
+type AuthentikUser struct {
+	Username     string   `json:"username"`
+	Email        string   `json:"email"`
+	Name         string   `json:"name"`
+	UID          string   `json:"uid"`
+	Groups       []string `json:"groups,omitempty"`
+	Entitlements []string `json:"entitlements,omitempty"`
+	JWT          string   `json:"-"`
+}
+
+// HasGroup reports whether the user belongs to the named group.
+func (u *AuthentikUser) HasGroup(group string) bool {
+	for _, g := range u.Groups {
+		if g == group {
+			return true
+		}
+	}
+	return false
+}

authentik_test.go

@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: EUPL-1.2
+
+package api_test
+
+import (
+	"testing"
+
+	api "forge.lthn.ai/core/go-api"
+)
+
+// ── AuthentikUser ──────────────────────────────────────────────────────
+
+func TestAuthentikUser_Good(t *testing.T) {
+	u := api.AuthentikUser{
+		Username:     "alice",
+		Email:        "alice@example.com",
+		Name:         "Alice Smith",
+		UID:          "abc-123",
+		Groups:       []string{"editors", "admins"},
+		Entitlements: []string{"premium"},
+		JWT:          "tok.en.here",
+	}
+
+	if u.Username != "alice" {
+		t.Fatalf("expected Username=%q, got %q", "alice", u.Username)
+	}
+	if u.Email != "alice@example.com" {
+		t.Fatalf("expected Email=%q, got %q", "alice@example.com", u.Email)
+	}
+	if u.Name != "Alice Smith" {
+		t.Fatalf("expected Name=%q, got %q", "Alice Smith", u.Name)
+	}
+	if u.UID != "abc-123" {
+		t.Fatalf("expected UID=%q, got %q", "abc-123", u.UID)
+	}
+	if len(u.Groups) != 2 || u.Groups[0] != "editors" {
+		t.Fatalf("expected Groups=[editors admins], got %v", u.Groups)
+	}
+	if len(u.Entitlements) != 1 || u.Entitlements[0] != "premium" {
+		t.Fatalf("expected Entitlements=[premium], got %v", u.Entitlements)
+	}
+	if u.JWT != "tok.en.here" {
+		t.Fatalf("expected JWT=%q, got %q", "tok.en.here", u.JWT)
+	}
+}
+
+func TestAuthentikUserHasGroup_Good(t *testing.T) {
+	u := api.AuthentikUser{
+		Groups: []string{"editors", "admins"},
+	}
+
+	if !u.HasGroup("admins") {
+		t.Fatal("expected HasGroup(admins) = true")
+	}
+	if !u.HasGroup("editors") {
+		t.Fatal("expected HasGroup(editors) = true")
+	}
+}
+
+func TestAuthentikUserHasGroup_Bad_Empty(t *testing.T) {
+	u := api.AuthentikUser{}
+
+	if u.HasGroup("admins") {
+		t.Fatal("expected HasGroup(admins) = false for empty user")
+	}
+}
+
+func TestAuthentikConfig_Good(t *testing.T) {
+	cfg := api.AuthentikConfig{
+		Issuer:       "https://auth.example.com",
+		ClientID:     "my-client",
+		TrustedProxy: true,
+		PublicPaths:  []string{"/public", "/docs"},
+	}
+
+	if cfg.Issuer != "https://auth.example.com" {
+		t.Fatalf("expected Issuer=%q, got %q", "https://auth.example.com", cfg.Issuer)
+	}
+	if cfg.ClientID != "my-client" {
+		t.Fatalf("expected ClientID=%q, got %q", "my-client", cfg.ClientID)
+	}
+	if !cfg.TrustedProxy {
+		t.Fatal("expected TrustedProxy=true")
+	}
+	if len(cfg.PublicPaths) != 2 {
+		t.Fatalf("expected 2 public paths, got %d", len(cfg.PublicPaths))
+	}
+}