Implement findOneAndReplace command

[maheshrajamani]

Replaces a single document based on the specified filter and sort. Returns a document in response.

{ "findOneAndReplace" : { "filter" : {filter clause}, "sort" : {sort clause}, "replacement" : {document to replace}, "options" : {"returnDocument" : "before/after"} } }

If upsert is true, insert the replacement document as new record.
if returnDocument is before return existing document, else return replaced document.

Validation: If the replacement document "_id" field is different from document read from the DB, throw error.

[vkarpov15]

Also worth noting: you can omit _id in the replacement. So if _id is in replacement, it should be exactly equal to the _id in the db. But if omitted, findOneAndReplace() will use the existing document's _id.

[maheshrajamani]

@johnsmartco My bad to have the upsert flag in the sample here. It's not supported for findOneAndReplace command.