Add headers in tests (#2329)

* Add headers in tests

...and fix RestJsonHttpWithEmptyBlobPayload

Signed-off-by: Daniele Ahmed <ahmeddan@amazon.de>

* style

Signed-off-by: Daniele Ahmed <ahmeddan@amazon.de>

* Remove tab

Signed-off-by: Daniele Ahmed <ahmeddan@amazon.de>

* ktlint

Signed-off-by: Daniele Ahmed <ahmeddan@amazon.de>

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Signed-off-by: Daniele Ahmed <ahmeddan@amazon.de>