Closes #11559: Implement config template rendering (#11769)

* WIP

* Add config_template field to Device

* Pre-fetch referenced templates

* Correct up_to_date callable

* Add config_template FK to Device

* Update & merge migrations

* Add config_template FK to Platform

* Add tagging support for ConfigTemplate

* Catch exceptions when rendering device templates in UI

* Refactor ConfigTemplate.render()

* Add support for returning plain text content

* Add ConfigTemplate model documentation

* Add feature documentation for config rendering

netbox/extras/api/views.py

@@ -5,6 +5,7 @@ from rest_framework import status
 from rest_framework.decorators import action
 from rest_framework.exceptions import PermissionDenied
 from rest_framework.permissions import IsAuthenticated
+from rest_framework.renderers import JSONRenderer
 from rest_framework.response import Response
 from rest_framework.routers import APIRootView
 from rest_framework.viewsets import ReadOnlyModelViewSet, ViewSet
@@ -19,10 +20,12 @@ from extras.scripts import get_script, get_scripts, run_script
 from netbox.api.authentication import IsAuthenticatedOrLoginNotRequired
 from netbox.api.features import SyncedDataMixin
 from netbox.api.metadata import ContentTypeMetadata
+from netbox.api.renderers import TextRenderer
 from netbox.api.viewsets import NetBoxModelViewSet
 from utilities.exceptions import RQWorkerNotRunningException
 from utilities.utils import copy_safe_request, count_related
 from . import serializers
+from .nested_serializers import NestedConfigTemplateSerializer
 
 
 class ExtrasRootView(APIRootView):
@@ -157,6 +160,35 @@ class ConfigContextViewSet(SyncedDataMixin, NetBoxModelViewSet):
     filterset_class = filtersets.ConfigContextFilterSet
 
 
+#
+# Config templates
+#
+
+class ConfigTemplateViewSet(SyncedDataMixin, NetBoxModelViewSet):
+    queryset = ConfigTemplate.objects.prefetch_related('data_source', 'data_file')
+    serializer_class = serializers.ConfigTemplateSerializer
+    filterset_class = filtersets.ConfigTemplateFilterSet
+
+    @action(detail=True, methods=['post'], renderer_classes=[JSONRenderer, TextRenderer])
+    def render(self, request, pk):
+        """
+        Render a ConfigTemplate using the context data provided (if any). If the client requests "text/plain" data,
+        return the raw rendered content, rather than serialized JSON.
+        """
+        configtemplate = self.get_object()
+        output = configtemplate.render(context=request.data)
+
+        # If the client has requested "text/plain", return the raw content.
+        if request.accepted_renderer.format == 'txt':
+            return Response(output)
+
+        template_serializer = NestedConfigTemplateSerializer(configtemplate, context={'request': request})
+        return Response({
+            'configtemplate': template_serializer.data,
+            'content': output
+        })
+
+
 #
 # Reports
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