assign_am: differnet button style for those AM with 0 slots, rather than simply full

Signed-off-by: Mattia Rizzolo <mattia@debian.org>

process/templates/process/assign_am.html

@@ -63,7 +63,9 @@ document.addEventListener("DOMContentLoaded", evt => { main(); });
         <form action="{% url 'process_assign_am' pk=process.pk %}" method="post">{% csrf_token %}
           <input type="hidden" name="am" value="{{am.lookup_key}}">
           <button
-          {% if am.stats_free == 0 %}
+          {% if am.slots == 0 %}
+            class="btn btn-sm btn-outline-secondary" data-toggle="tooltip" title="This AM has no slots at all"
+          {% elif am.stats_free == 0 %}
             class="btn btn-sm btn-secondary" data-toggle="tooltip" title="This AM has no free slots"
           {% else %}
             {% if am.person.status == "dd_u" and process.applying_for == "dd_nu" %}