feat: default to charset=utf-8 for text content type

[PureWhiteWu]

Motivation

When using axum, I found that if I returned content in non-English(e.g. Chinese), then all browsers (include Chrome, Safari, Firefox) will display unreadable chars.

After investigating, I found that this is because axum only returns Content-Type: text/plain instead of Content-Type: text/plain; charset=utf-8.

I think adding charset=utf-8 as the default charset for text content type makes sense.

Solution

I added charset=utf-8 as the default charset for text content type and used the mime crate to avoid repeat and hard code of header values.

[davidpdrsn]

Thanks! This looks good to me.

@jplatte Do you wanna take a quick look as well?

[jplatte]

Looks good to me as well. I was a little worried about the extra dependency at first but I've had a quick skim of its docs & source and it really seems minimal (nothing like mime guessing based on magic bytes or file extensions in there) and is maintained by seanmonstar so doesn't even increase the potential for supply-chain attacks either.

[davidpdrsn]

One more thing I thought off: We should probably mention this in the changelog.

[PureWhiteWu]

I've fixed the comment and added the changelog

[PureWhiteWu]

@davidpdrsn Hi, thanks for your review!
You may need to approve the workflow for this pr~

[PureWhiteWu]

@davidpdrsn
Sorry for the mistake. Should be fine now.
I've tested locally.