[Feature] Simple template extension mechanism (#361)

Co-authored-by: Tim Lorsbach <tim@lorsba.ch>
Reviewed-on: enviPath/enviPy#361

templates/collections/compounds_paginated.html

@@ -1,21 +1,34 @@
 {% extends "collections/paginated_base.html" %}
+{% load envipytags %}
 
 {% block page_title %}Compounds{% endblock %}
 
 {% block action_button %}
-  {% if meta.can_edit %}
-    <button
-      type="button"
-      class="btn btn-primary btn-sm"
-      onclick="document.getElementById('new_compound_modal').showModal(); return false;"
-    >
-      New Compound
-    </button>
-  {% endif %}
+  <div class="flex items-center gap-2">
+    {% if meta.can_edit %}
+      <button
+        type="button"
+        class="btn btn-primary btn-sm"
+        onclick="document.getElementById('new_compound_modal').showModal(); return false;"
+      >
+        New Compound
+      </button>
+    {% endif %}
+    {% epdb_slot_templates "epdb.actions.collections.compound" as action_button_templates %}
+
+    {% for tpl in action_button_templates %}
+      {% include tpl %}
+    {% endfor %}
+  </div>
 {% endblock action_button %}
 
 {% block action_modals %}
   {% include "modals/collections/new_compound_modal.html" %}
+  {% epdb_slot_templates "modals.collections.compound" as action_modals_templates %}
+
+  {% for tpl in action_modals_templates %}
+    {% include tpl %}
+  {% endfor %}
 {% endblock action_modals %}
 
 {% block description %}