Adding Live 2fa capacity

* Some requests may be sensitive enough to require a secondary
two-factor authorization on the spot
* Examples: changing password, changing email address, viewing API
tokens etc
* This creates a core handler that can attach to any Auth-able method
which will require a "twofactorcode" query param before processing

models/auth.go

@@ -5,6 +5,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/google/uuid"
 	"github.com/pquerna/otp/totp"
 	"golang.org/x/crypto/bcrypt"
 )
@@ -55,6 +56,12 @@ func (a *Auth) CheckPassword(pass string) error {
 	return bcrypt.CompareHashAndPassword([]byte(a.PasswordHash), []byte(pass))
 }
 
+type TotpUsage struct {
+	LoginUid uuid.UUID `gorm:"index"`
+	Used     time.Time
+	Code     string `gorm:"index"`
+}
+
 func (a *Auth) ValidateTwoFactor(tfCode string, stamp time.Time) error {
 	if tfCode == "" && a.TwoFactorSecret != "" {
 		return errors.New("requires 2FA")