respondUnflushed

    pub fn respondUnflushed(
        request: *Request,
        content: []const u8,
        options: RespondOptions,
    ) ExpectContinueError!void {
        assert(options.status != .@"continue");
        if (std.debug.runtime_safety) {
            for (options.extra_headers) |header| {
                assert(header.name.len != 0);
                assert(std.mem.findScalar(u8, header.name, ':') == null);
                assert(std.mem.findPosLinear(u8, header.name, 0, "\r\n") == null);
                assert(std.mem.findPosLinear(u8, header.value, 0, "\r\n") == null);
            }
        }
        try writeExpectContinue(request);

        const transfer_encoding_none = (options.transfer_encoding orelse .chunked) == .none;
        const server_keep_alive = !transfer_encoding_none and options.keep_alive;
        const keep_alive = request.discardBody(server_keep_alive);

        const phrase = options.reason orelse options.status.phrase() orelse "";

        const out = request.server.out;
        try out.print("{s} {d} {s}\r\n", .{
            @tagName(options.version), @backingInt(options.status), phrase,
        });

        switch (options.version) {
            .@"HTTP/1.0" => if (keep_alive) try out.writeAll("connection: keep-alive\r\n"),
            .@"HTTP/1.1" => if (!keep_alive) try out.writeAll("connection: close\r\n"),
        }

        if (options.transfer_encoding) |transfer_encoding| switch (transfer_encoding) {
            .none => {},
            .chunked => try out.writeAll("transfer-encoding: chunked\r\n"),
        } else {
            try out.print("content-length: {d}\r\n", .{content.len});
        }

        for (options.extra_headers) |header| {
            var vecs: [4][]const u8 = .{ header.name, ": ", header.value, "\r\n" };
            try out.writeVecAll(&vecs);
        }

        try out.writeAll("\r\n");

        if (request.head.method != .HEAD) {
            const is_chunked = (options.transfer_encoding orelse .none) == .chunked;
            if (is_chunked) {
                if (content.len > 0) try out.print("{x}\r\n{s}\r\n", .{ content.len, content });
                try out.writeAll("0\r\n\r\n");
            } else if (content.len > 0) {
                try out.writeAll(content);
            }
        }
    }