Escape content with `<![CDATA[ xxx ]]>`

[ThibaudDauce]

Hi,

I've created an item in my feed with

        feed = Atom1Feed(
            _("Latest APIs"), description=None, feed_url=request.url, link=request.url_root
        )

            feed.add_item(
                dataservice.title,
                unique_id=dataservice.id,
                description=dataservice.description,
                content=md(dataservice.description),
                author_name=author_name,
                author_link=author_uri,
                link=dataservice.url_for(),
                updateddate=dataservice.metadata_modified_at,
                pubdate=dataservice.created_at,
            )

but the content is not correctly encoded for HTML. The W3C validator reports:

[line 6](https://validator.w3.org/feed/check.cgi?url=https%3A%2F%2Fwww.data.gouv.fr%2Ffr%2Fdatasets%2Frecent.atom#l6), column 225: Undefined content element: div (6 occurrences) [[help](https://validator.w3.org/feed/docs/error/UndefinedElement.html)]

    ... ridiques.</summary><content type="html"><div class="markdown"><p>L'arrêt ...
                                                 ^

[line 39](https://validator.w3.org/feed/check.cgi?url=https%3A%2F%2Fwww.data.gouv.fr%2Ffr%2Fdatasets%2Frecent.atom#l39), column 339: XML parsing error: <unknown>:39:339: mismatched tag [[help](https://validator.w3.org/feed/docs/error/SAXError.html)]

    ... -2022-357578" rel="nofollow">23.06</a></h2></div></content></entry><entr ...

Is it possible to escape the content with CDATA?