* extract http protocol into protocol.zig, as it is shared between client and server
* coalesce Request and Response back into Client.zig, they don't contain
any large chunks of code anymore
* http.Server is implemented as basic as possible, a simple example below:
```zig
fn handler(res: *Server.Response) !void {
while (true) {
defer res.reset();
try res.waitForCompleteHead();
res.headers.transfer_encoding = .{ .content_length = 14 };
res.headers.connection = res.request.headers.connection;
try res.sendResponseHead();
_ = try res.write("Hello, World!\n");
if (res.connection.closing) break;
}
}
pub fn main() !void {
var server = Server.init(std.heap.page_allocator, .{ .reuse_address = true });
defer server.deinit();
try server.listen(try net.Address.parseIp("127.0.0.1", 8080));
while (true) {
const res = try server.accept(.{ .dynamic = 8192 });
const thread = try std.Thread.spawn(.{}, handler, .{res});
thread.detach();
}
}
```
Common headers in a response are:
Content-Encoding: gzip
Transfer-Encoding: chunked
We used to return `HttpHeadersInvalid` if a `Transfer-Encoding` header
was received while the compression was already set.
However, Transfer-Encoding may not include compression. We should
only return an error if we are setting a value that was already set.
Fixes compatibility with a bunch of websites.
