response headers support custom encoding

[0b1Kenobi]

Hi~ When i try to return a FileResponse with Chinese filename, i got such error:

UnicodeEncodeError: 'latin-1' codec can't encode character '\u6708' in position 32: ordinal not in range(256)

Then i found all header items will be encode with latin-1, after i change it manually to utf-8, my problem was solved.

e.g.

• responses.Response.init_headers, line 63

raw_headers = [
    (k.lower().encode("latin-1"), v.encode("latin-1"))
    for k, v in headers.items()
]

So may be it should encode with self.charset or give a custom parameter so that i can choose encoding to utf-8?

Thx for the great project~

[CyberQin]

#792 only solves FileReponse,but it still a problem in streamreponse.