Decouple totp from users table by moving to totp_credentials table

* this allows implementation of other mfa schemes in the future (webauthn)
* also makes key management easier and enforces one totp credentials per user on db-level

management/templates/two-factor-auth.html

@@ -31,7 +31,7 @@
     }
 </style>
 
-<h2>Two Factor Authentication</h2>
+<h2>Two-Factor Authentication</h2>
 
 <div class="twofactor">
     <div class="loading-indicator">Loading...</div>