"content-type" header behavior from external processes is poorly defined

When returning headers from an external process, the behavior depends on capitalization, and is radically different in each case.

Consider the external process return

a: { "code":200, "json":

{ "hello":"world" }

, "headers": {} }.

If returned as (a), the server serves

{ "hello":"world" }

with header "Content-Type: application/json".

If the json is modified to

b: { "code":200, "json":

{ "hello":"world" }

, "headers":

{"Content-type":"text/plain"}

}
c: { "code":200, "json":

{ "hello":"world" }

, "headers":

{"content-type":"text/plain"}

}

If returned as (b) or (c), the server serves

{ "hello":"world" }

with header "Content-Type: text/plain, application/json".

If the json is modified to

d: c: { "code":200, "json":

{ "hello":"world" }

, "headers":

{"Content-Type":"text/plain"}

}

If returned as (d), the server serves

{ "hello":"world" }

with header "Content-Type: text/plain".

There should be one well defined behavior when a "content-type" header is returned from an external process.

To reproduce this error, setup an external process and return json strings as specified above.