Feat check account existence

Handle and display account creation error if relevant

app/templates/errors/registration_failed.html

@@ -8,20 +8,7 @@
 
     <h2>Something went wrong...</h2>
     <p>
-       Redirecting back to sign-in page in <span id="countdown"></span> seconds.
-    <script>
-    function sleep(ms) {
-        return new Promise(resolve => setTimeout(resolve, ms));
-    }
-    //todo: get seconds to update as time passes
-    var count = 6;
-    for (count; count >=0; count--) {
-        document.getElementById("countdown").innerText = count;
-        sleep(1000);
-
-    }
-    </script>
-
+       Redirecting back to sign-in page in 5 seconds.
     </p>
 </body>
 </html>
\ No newline at end of file