integration of the new MVC for subproject_addresses

app/views/subproject_addresses/_form.html.erb

@@ -0,0 +1,24 @@
+<%= form_with(model: subproject_address) do |form| %>
+  <% if subproject_address.errors.any? %>
+    <div style="color: red">
+      <h2><%= pluralize(subproject_address.errors.count, "error") %> prohibited this client from being saved:</h2>
+
+      <ul>
+        <% subproject_address.errors.each do |error| %>
+          <li><%= error.full_message %></li>
+        <% end %>
+      </ul>
+    </div>
+  <% end %>
+
+  <% [:streetname, :zipcode, :city, :country].each do |attrib| %>
+  <div>
+    <%= form.label attrib, style: "display: block" %>
+    <%= form.text_field attrib %>
+  </div>
+  <% end %>
+
+  <div>
+    <%= form.submit %>
+  </div>
+<% end %>