Adds a new InvenTreePluginMixin mixin class for enabling custom plugin rendering on a page

- Any view which needs custom plugin code must implement this mixin
- Initially implement for the PartDetail page

InvenTree/templates/panel/plugin_javascript.html

@@ -0,0 +1,10 @@
+{% if plugin_panels %}
+// Run custom javascript when plugin panels are loaded
+{% for panel in plugin_panels %}
+{% if panel.javascript %}
+onPanelLoad('{{ panel.key }}', function() {
+{{ panel.javascript | safe }}
+});
+{% endif %}
+{% endfor %}
+{% endif %}

InvenTree/templates/panel/plugin_menu_items.html

@@ -0,0 +1,3 @@
+{% for panel in plugin_panels %}
+{% include "sidebar_item.html" with label=panel.key text=panel.title icon=panel.icon %}
+{% endfor %}

InvenTree/templates/panel/plugin_panels.html

@@ -0,0 +1,18 @@
+{% for panel in plugin_panels %}
+
+<div class='panel panel-hidden' id='panel-{{ panel.key }}'>
+    <div class='panel-heading'>
+        <div class='d-flex flex-wrap'>
+            <h4>{{ panel.title }}</h4>
+            {% include "spacer.html" %}
+            <div class='btn-group' role='group'>
+                <!-- TODO: Implement custom action buttons for plugin panels -->
+            </div>
+        </div>
+    </div>
+    <div class='panel-content'>
+        {{ panel.content | safe }}
+    </div>
+</div>
+
+{% endfor %}