Split welcome email between html and text version

src/mail_templates/welcome_user-html.ejs

@@ -0,0 +1,29 @@
+<center>
+
+<img src="<%= cloudronAvatarUrl %>" width="128px" height="128px"/>
+
+<h3>Hi <%= user.displayName || user.username || user.email %>,</h3>
+
+<h2>Welcome to <%= cloudronName %>!</h2>
+
+<p>
+    <a href="<%= inviteLink %>">Get started</a>.
+</p>
+
+<br/>
+<br/>
+
+<div style="font-size: 10px; color: #333333; background: #ffffff;">
+    <% if (invitor && invitor.email) { %>
+        You are receiving this email because you were invited by <%= invitor.email %>.
+    <% } %>
+
+    <br/>
+
+        Please note that the invite link will expire in 7 days.
+    <br/>
+
+    Powered by <a href="https://cloudron.io">Cloudron</a>
+</div>
+
+</center>