Apache CouchDB agent changelog

New: Apache CouchDB source and target agent for CouchDB 3.3, 3.4 and 3.5, on a single node or on a cluster. It talks to CouchDB over its HTTP JSON API, with no vendor SDK. One entity is one database, under the schema _default. As a source it takes a snapshot that lists the ids from the _changes feed and reads the documents with parallel _bulk_get requests (94,000 documents per second with 16 requests at a time, against 28,000 for _all_docs), resumes an interrupted snapshot from the feed position it had safely reached, and follows the _changes feed for CDC, replaying the changes made during the snapshot. Deletes carry only the _id, so the entity key must be _id, and design documents are skipped. As a target it writes with parallel _bulk_docs requests, looks up revisions, retries conflicts, writes tombstones for deletes, merges partial changes into the stored document and creates databases with the number of shards you choose, the main lever of the write throughput (15,000 documents per second with 2 shards, 81,000 with 32 on a single node). Attachments and purges are not replicated;