[Feature Request] Calcurse-caldav external password support

[refacto]

I really like the functionality of calcurse-caldav, the only problem I have is that I don't like storing my password in a plain text file.
What I'm requesting for is that it should be possible to get the password for calcurse-caldav via external command, so that it'd be possible to issue something like 'pass ls calendar'. That way, passwords aren't stored in an unencrypted fashion.

[lfos]

You can now set the password using the CALCURSE_CALDAV_PASSWORD environment variable; see 9be2c10 (calcurse-caldav: Read password from env variable, 2017-11-10) for details.