feature: apply encoding when parse feilds

[merik-chen]

Please kindly review the PR due to the multi-byte field name not getting properly parsed.

[yortus]

Thanks for the contribution @merik-chen! I've pushed some changes to keep all the encoding selection logic in one place and use it consistently.

Do you have a file with non-latin-1 field names that can be added to the test fixtures, so we can add a test case for this?

[merik-chen]

@yortus Sorry for the late replies. I added a test fixture with non-Latin-1 headers.

I can pass the reading test but failed the writing one.

It seems like still related to the header encoding problem after writing data to the file. seek your help to deal with it.

[yortus]

Sorry for the delay @merik-chen. Thanks for adding the test file - it revealed another field name encoding bug which I've fixed. Merging now, thanks very much for your contribution!