An action block that sends a response to an incoming HTTP request from prior a HTTP serve block.
The fiber will pause until the response has been sent.
The response content body and response content path can both be arrays thereof,
the elements of both are interleaved beginning with body then file, body and so on.
If only one array is used, or one is longer that the other, the (remaining) elements are simply concatenated. null
elements are ignored.
This can be used to concatenate files before upload, or send a multipart body.
"Content-Disposition"
.