Response.header.content-type can not be parsed

Sorry!
The hyphen is not a valid character in a FEEL variables name:
[Variables | Camunda 8 Docs]

See also:

Thanks for the hint from @nathan.loding!
The correct FEEL expression is now:

{
 content_type: get value(response.headers, “Content-Type”)
}

Again, as mentioned in my previous post, this is case-sensitive!
This FEEL expression has been successfully tested.