ordering of set_header and body_string matters

[prabirshrestha]

This doesn't set the response header has text/html

 let res = Response::new(StatusCode::Ok)
        .set_header("content-type".parse().unwrap(), "text/html;charset=utf-8")
        .body_string("Hello<br/>".to_owned());

This one does set it correctly.

 let res = Response::new(StatusCode::Ok)
        .body_string("Hello<br/>".to_owned())
        .set_header("content-type".parse().unwrap(), "text/html;charset=utf-8");

tide = "0.8.0"

[Fishrock123]

The docs for res.body_string explicitly say

The encoding is set to text/plain; charset=utf-8.

I do think it would probably be more developer friendly for this function to check if the content-type header has been set yet or not, though.

Also, if I may, recommend setting the content type through res.set_mime, like tide does internally. See https://docs.rs/mime/0.3.16/mime/index.html#constants.

res.set_mime(mime::TEXT_PLAIN_UTF_8)

[Fishrock123]

Also, it's not immediately clear but res.set_body(string) should also work. res.body_string() just does that internally.

[prabirshrestha]

Seems like set_body need to return self to make it easy to chain else need to create temp mutable vars.

[Fishrock123]

See also: #562