Apply transformation to the record and return another record object (which may be record itself) or null,
corresponding to a map or filter operation respectively.
A transformation must not mutate objects reachable from the given record
(including, but not limited to, Headers,
Structs, Lists, and Maps).
If such objects need to be changed, a new ConnectRecord should be created and returned.
The implementation must be thread-safe.
Configuration specification for this transformation.
Signal that this transformation instance will no longer will be used.