Add kwargs into insert method #2169

[erdenezul]

Closes #2169

[bagerard]

I see a potential bug related to the following code (that is a bit below in this method):

        # Apply inserted_ids to documents
        for doc, doc_id in zip(docs, ids):
            doc.pk = doc_id

In case you provide ordered=False and it raises an error (e.g if you try to insert 2 times a document with same pk), that piece of code won't be reached, leaving the mongoengine documents without id's. Instead of relying on zip to get the corresponding id, we could rely on the raw dict that actually gets updated with the id by pymongo (see this post). Now since it will raise an error anyway, perhaps it could be acceptable to not set the id on the Documents instances. What do you think?

[bagerard]

btw in case of successful unordered insert, I'm also unsure if we could rely on zip , as I don't know if we can rely on the order of inserted_result.inserted_ids