🏷️(backend) add body type on generate-document endpoint

We were converting from markdown to html, but the
frontend can provide the body in html format, so
wa can avoid the conversion.

Solution:
Add body type on generate-document endpoint
to allow to choose between markdown and html.

src/backend/core/api/serializers.py

@@ -153,4 +153,10 @@ class TemplateSerializer(BaseResourceSerializer):
 class DocumentGenerationSerializer(serializers.Serializer):
     """Serializer to receive a request to generate a document on a template."""
 
-    body = serializers.CharField(label=_("Markdown Body"))
+    body = serializers.CharField(label=_("Body"))
+    body_type = serializers.ChoiceField(
+        choices=["html", "markdown"],
+        label=_("Body type"),
+        required=False,
+        default="html",
+    )

src/backend/core/api/viewsets.py

@@ -372,9 +372,10 @@ class TemplateViewSet(
             )
 
         body = serializer.validated_data["body"]
+        body_type = serializer.validated_data["body_type"]
 
         template = self.get_object()
-        pdf_content = template.generate_document(body)
+        pdf_content = template.generate_document(body, body_type)
 
         response = FileResponse(BytesIO(pdf_content), content_type="application/pdf")
         response["Content-Disposition"] = f"attachment; filename={template.title}.pdf"