Do not auto-remove content headers for body-less status codes

[LJ1102]

According to RFC 2616 (HTTP/1.1 spec) a HEAD request is supposed to return exactly the same entity-headers as a GET request but no body, imho responding to such a request with a 204 status code seems reasonable, thus we should not remove any headers but only ensure that no body is sent.

[LJ1102]

I did some more digging and in fact RFC 7230 specifies the following:

Transfer-Encoding MAY be sent in a response to a HEAD request or in a 304 (Not Modified) response

A server MAY send a Content-Length header field in a 304 (Not Modified) response to a conditional GET request

A server MUST NOT send a Content-Length header field in any response with a status code of 1xx (Informational) or 204 (No Content).

So I altered my changes (and adjusted the unit tests) to be compliant to that, so that with a 304 we leave the content-headers untouched, but on 204 we remove them.

[Bishal07-glitch]

// freshness
if (req.fresh) this.statusCode = 304;

// strip irrelevant headers
if (204 === this.statusCode || 304 === this.statusCode) {
// remove content headers for 204
if (this.statusCode === 204) {
this.removeHeader('Content-Type');
this.removeHeader('Content-Length');
this.removeHeader('Transfer-Encoding');
chunk = ''; // Clear the response body
}

// alter headers for 205
if (this.statusCode === 205) {
    this.set('Content-Length', '0');
    this.removeHeader('Transfer-Encoding');
    chunk = ''; // Clear the response body
}

// Handling HEAD request
if (req.method === 'HEAD' || this.statusCode === 204 || this.statusCode === 205 || this.statusCode === 304) {
    // Skip sending the body for HEAD request or certain status codes
    this.end();
} else {
    // Respond with the actual content
}

}