Fix #152: encoding name of addresses in utf-8

[tomyeh]

@close2 I fixed #152 by encoding name to utf-8+base64.

Note:

1. It doesn't support 2.12 yet
2. I introduced Address.sanitizedName and sanitizedAddress for application to override (which I need it).
3. I made Address's name and mailAddress as final, so const Address is possible.
   • I know you revoked it when merging the code. But, I think the version of 2.12 is a good opportunity to drop some backward compatible code.
   • Make them final have two advantages: 1) easy to override, 2) able to use const to make the code a bit more efficient.

Item 2 and 3 are not necessary. If you don't like it you can revoke it.

[close2]

LGTM

Do you want me to wait for a 2.12 version?

The null safety version would have been a perfect opportunity to change the interface. Bad luck. I'll just bump the version to 5.0.0

[tomyeh]

Please upgrade it to 2.12. I don't plan to upgrade our apps to 2.12 yet.

[close2]

Please upgrade it to 2.12. I don't plan to upgrade our apps to 2.12 yet.

Will do.

[close2]

Hi @tomyeh !

I've created a PR where your changes are merged with the current 4.0.0 version: https://github.com/kaisellgren/mailer/pull/170

This PR is currently more or less untested.

Your feedback is welcome.