Add 'let' parameter support to the findAndModify command. Currently this is only supported for standalone environments.
Description of Linked Ticket
Building on top of work in
SERVER-46708 and SERVER-46709, add support for the findAndModify command. Again, focus on unsharded deployments here.
Scope of changes
Impact to Other Docs
MVP (Work and Date)
Resources (Scope or Design Docs, Invision, etc.)