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/forms/model_forms.py

@@ -18,6 +18,7 @@ from virtualization.models import Cluster, ClusterGroup, ClusterType
 
 __all__ = (
     'ConfigContextForm',
+    'ConfigTemplateForm',
     'CustomFieldForm',
     'CustomLinkForm',
     'ExportTemplateForm',
@@ -269,6 +270,34 @@ class ConfigContextForm(BootstrapMixin, SyncedDataMixin, forms.ModelForm):
         return self.cleaned_data
 
 
+class ConfigTemplateForm(BootstrapMixin, SyncedDataMixin, forms.ModelForm):
+    tags = DynamicModelMultipleChoiceField(
+        queryset=Tag.objects.all(),
+        required=False
+    )
+    template_code = forms.CharField(
+        required=False,
+        widget=forms.Textarea(attrs={'class': 'font-monospace'})
+    )
+
+    fieldsets = (
+        ('Config Template', ('name', 'description', 'environment_params', 'tags')),
+        ('Content', ('data_source', 'data_file', 'template_code',)),
+    )
+
+    class Meta:
+        model = ConfigTemplate
+        fields = '__all__'
+
+    def clean(self):
+        super().clean()
+
+        if not self.cleaned_data.get('template_code') and not self.cleaned_data.get('data_file'):
+            raise forms.ValidationError("Must specify either local content or a data file")
+
+        return self.cleaned_data
+
+
 class ImageAttachmentForm(BootstrapMixin, forms.ModelForm):
 
     class Meta: