Password forms improvements

[spaze]

Well, I'm the only one using the login forms on this site but still wanted to try these.

• Raise min length to 15 chars
• Help password managers understand the form fields
• Indicate which account is the password being changed for
• Tell 1Password to generate a bit longer+stronger password by default

TIL the passwordrules attribute thanks to this great @ScottHelme's blog post https://scotthelme.co.uk/boosting-account-security-pwned-passwords-and-zxcvbn/

Here are some helpful links:

• Design your website to work best with 1Password
• Password Rules Validation Tool by Apple, apparently supported in Safari since 2018 (Safari 12)
• Proposal: HTML passwordrules attribute whatwg/html#3518

This is a companion to

• Add well-known URL for changing passwords in admin #89

And there's a followup in

• passwordrules attribute on username makes no sense #91