Add support for json output in subkey (#4882)

* Add support for json output in subkey

* Updates as per code review

* Apply suggestions from code review

Co-Authored-By: Nikolay Volf <[email protected]>

* Apply suggestions from code review

Co-Authored-By: Bastian Köcher <[email protected]>

* Clean up error handler as per code review

* Apply suggestions from code review

Co-Authored-By: Marcio Diaz <[email protected]>

* Fix compilation error

* Remove accidental file commit

Co-authored-by: Nikolay Volf <[email protected]>
Co-authored-by: Bastian Köcher <[email protected]>
Co-authored-by: Marcio Diaz <[email protected]>