Just for the record, don't know if the corner case was taken into account previously.
If a user tries to rename a collection to itself, starting from now an IllegalOperation is thrown. Before, a misleading NamespaceNotFound exception was thrown.
Description of Linked Ticket
If the collection exists, the collection version must be returned in a best-effort fashion, without acquiring any lock.
If the collection exists but dropTarget=true, an `IllegalOptions` error must be returned.
If the collection doesn't exist, a `NamespaceNotFound` error is already thrown both in case of RS or sharded cluster.
Scope of changes
Impact to Other Docs
MVP (Work and Date)
Resources (Scope or Design Docs, Invision, etc.)