Updated the register to only allow to create users if they have a code available

src/email/templates/main.handlebars

@@ -11,13 +11,20 @@
   <img src="/logo_title.png" class="w-48 h-48 self-center" />
   <div>
     <span>Hello future {{type}} of <b>EnCoach</b>,</span><br />
-    <span>You have been invited to register at <a href="https://encoach.com">EnCoach</a> to become a
+    <span>You have been invited to register at <a href="https://encoach.com/register?code={{code}}">EnCoach</a> to
+      become a
       {{type}}!</span><br />
     <span>Please use the following code when registering:</span>
   </div>
+  <br />
+  <br />
+  <a href="https://encoach.com/register?code={{code}}"></a>
   <span class="self-center p-4 px-12 text-lg text-[#]" style="background-color: #D5D9F0; color: #353338">
     <b>{{code}}</b>
   </span>
+  </a>
+  <br />
+  <br />
   <div>
     <span>Thanks, <br /> Your EnCoach team</span>
   </div>