🗃️(backend) export to docx

We can now export our document to a docx file.
This is done by converting the html to a docx
file using the pypandoc and pandoc library.
We added the "format" param to the
generate-document endpoint, "format" accept
"pdf" or "docx" as value.

src/backend/core/api/serializers.py

@@ -180,6 +180,12 @@ class DocumentGenerationSerializer(serializers.Serializer):
         required=False,
         default="html",
     )
+    format = serializers.ChoiceField(
+        choices=["pdf", "docx"],
+        label=_("Format"),
+        required=False,
+        default="pdf",
+    )
 
 
 class InvitationSerializer(serializers.ModelSerializer):