Implementing hook for dynamically adding fields to mapping

[safwanrahman]

For having the mapping dynamically generated, we need to have a hook that will get the fields dynamically. I believe, its needed by django-elasticsearch-dsl to generete Elasticsearch DSL mapping dynamically from Django model.
@honzakral As you have mentioned in your comment #930 (comment), is it a correct approach to have a hook for django-elasticsearch-dsl? I am currently trying to upgrade it for elasticsearch-dsl-py>6.1.0

[safwanrahman]

Seems like it will not work! 😞

[safwanrahman]

@honzakral Do you have any idea how to accomplish the feature to have a hook to dynamically generate the mapping?

[honzakral]

There should be no need for an extra hook to add fields, you can always access the Mapping by doing DocClass._doc_type.mapping or DocClass._index._mapping and then you can easily call the .field() method there to add additional fields.

The only issue now is that if you add a field to the DocClass._doc_type.mapping it will not propagate up to the Index at DocClass._index (unless you create a new one) so DocClass.init() won't take it into account... I fixed that in ceac532

Hope this helps!