feat(auth): implement user and device authentication

backend-api/internal/domain/auth_test.go

@@ -0,0 +1,63 @@
+package domain
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestNormalizeUsernameAndValidateUserInput(t *testing.T) {
+	if got := NormalizeUsername("  Admin.User  "); got != "admin.user" {
+		t.Fatalf("NormalizeUsername() = %q", got)
+	}
+	if err := ValidateUserInput(
+		"admin.user",
+		"strong-password",
+		UserRoleAdmin,
+	); err != nil {
+		t.Fatalf("ValidateUserInput(valid) error = %v", err)
+	}
+	for name, input := range map[string]struct {
+		username string
+		password string
+		role     UserRole
+	}{
+		"blank username": {" ", "password", UserRoleAdmin},
+		"blank password": {"admin", "", UserRoleAdmin},
+		"short password": {"admin", "short", UserRoleAdmin},
+		"invalid password UTF-8": {
+			"admin",
+			string([]byte{0xff, 0xfe, 0xfd}),
+			UserRoleAdmin,
+		},
+		"oversized password": {
+			"admin",
+			strings.Repeat("x", MaxPasswordBytes+1),
+			UserRoleAdmin,
+		},
+		"invalid role": {"admin", "password", "AUDITOR"},
+	} {
+		t.Run(name, func(t *testing.T) {
+			if err := ValidateUserInput(
+				input.username,
+				input.password,
+				input.role,
+			); err == nil {
+				t.Fatal("ValidateUserInput() error = nil")
+			}
+		})
+	}
+}
+
+func TestValidateDeviceName(t *testing.T) {
+	if err := ValidateDeviceName("Test device"); err != nil {
+		t.Fatalf("ValidateDeviceName(valid) error = %v", err)
+	}
+	if err := ValidateDeviceName(" "); err == nil {
+		t.Fatal("ValidateDeviceName(blank) error = nil")
+	}
+	if err := ValidateDeviceName(
+		strings.Repeat("x", MaxDeviceNameBytes+1),
+	); err == nil {
+		t.Fatal("ValidateDeviceName(oversized) error = nil")
+	}
+}