Request from the community

https://www.mongodb.com/community/forums/t/support-for-custom-deletewritemode-strategies-in-kafka-sink/175547

we like to persist has a String-Key and a JSON payload. The id for the MongoDB is part of the JSON payload.  when we receive a tombstone event, we’d like to delete all records that have the key of the topic in a certain field. 

Currently this is not possible due to -

1. Writing is not possible, since the connector fails on the first tombstone event and stops afterwards
2. Delete is not possible, since there is no support for substituting the model for the delete case in a fashion similiar to writemodel.strategy

PR=https://github.com/mongodb/mongo-kafka/pull/108/files