Contact email: specify username == email

templates/email/org_contacts/email_contact_for_activation.html

@@ -4,7 +4,7 @@
     Many thanks for sponsoring SciPost. We have now created a personal account for you on scipost.org, which will allow you to access all relevant information and functionalities related to sponsoring.
 </p>
 <p>
-    In order to activate your account, please navigate to <a href="https://scipost.org{% url 'organizations:activate_account' contact.activation_key %}?email={{contact.user.email}}">this link</a>. You will be asked to choose a password, after which you will be able to login.
+    In order to activate your account, please navigate to <a href="https://scipost.org{% url 'organizations:activate_account' contact.activation_key %}?email={{contact.user.email}}">this link</a>. You will be asked to choose a password, after which you will be able to login (your username being defined as your email address).
 </p>
 <p>
     After logging in, you will find a “Org dashboard” link in the top menu, which will take you to your info page.