Closes #13368: Report installed plugins during server error (#13387)

* Introduce get_installed_plugins() utility

* Extend 500 error template to list installed plugins

* Move get_plugin_config() to extras.plugins.utils

netbox/extras/plugins/utils.py

@@ -0,0 +1,37 @@
+from django.apps import apps
+from django.conf import settings
+from django.core.exceptions import ImproperlyConfigured
+
+__all__ = (
+    'get_installed_plugins',
+    'get_plugin_config',
+)
+
+
+def get_installed_plugins():
+    """
+    Return a dictionary mapping the names of installed plugins to their versions.
+    """
+    plugins = {}
+    for plugin_name in settings.PLUGINS:
+        plugin_name = plugin_name.rsplit('.', 1)[-1]
+        plugin_config = apps.get_app_config(plugin_name)
+        plugins[plugin_name] = getattr(plugin_config, 'version', None)
+
+    return dict(sorted(plugins.items()))
+
+
+def get_plugin_config(plugin_name, parameter, default=None):
+    """
+    Return the value of the specified plugin configuration parameter.
+
+    Args:
+        plugin_name: The name of the plugin
+        parameter: The name of the configuration parameter
+        default: The value to return if the parameter is not defined (default: None)
+    """
+    try:
+        plugin_config = settings.PLUGINS_CONFIG[plugin_name]
+        return plugin_config.get(parameter, default)
+    except KeyError:
+        raise ImproperlyConfigured(f"Plugin {plugin_name} is not registered.")