Setting Web scenario headers through API request

[dryang]

Both string and array of HTTP fields types are allowed for headers and variables fields of both web scenario and web scenario step object.
String data type for headers and variables is deprecated and will be removed in future versions.

I'm able to create web scenario with headers when I'm using string in the json payload, but any combination of key value for header field gives me various errors.
Can you please post an example, how to correctly pass "HTTP fields" as an array.