Add result filename to output fields from "TextFileOutput"

[AlexLogov]

If we add "filename" field in the output fields for transform "TextFileOutput" than it can be used in pipeline.

In this transform filename can be dynamic change (add timestamp or by spliting) , byt filename not visible into pipeline. There is no way to find out the file name, save it, etc. With save relation to current row.

May I suggest a pull request with this change?

[hansva]

Of course! we are always happy with PR's that fix or implement features.
We have implemented features so anyone can "claim" a ticket they are working on, in this case you could use the .take-issue command on #4697 to assign it to yourself.