ovpn parser ignores auth-user-pass directive

[cachebag]

part of #288.

the .ovpn parser in core/ovpn_parser/parser.rs doesn't handle the auth-user-pass directive. this is one of the most common directives in real-world .ovpn files — it tells the client that the server requires username/password authentication.

because of this, TryFrom<OvpnFile> for OpenVpnConfig always sets auth_type: None, so imported configs don't know whether password auth is required. a user importing a .ovpn file that has auth-user-pass will get a config that doesn't prompt for or include credentials.

changes

• add auth_user_pass: bool field to OvpnFile
• parse auth-user-pass directive in the lexer/parser (with optional file path argument, which we can ignore for now — NM handles interactive prompts)
• in TryFrom<OvpnFile>, infer auth_type from the combination of auth_user_pass and cert presence:
  • auth_user_pass + certs → PasswordTls
  • auth_user_pass + no certs → Password
  • no auth_user_pass + certs → Tls
  • neither → None (same as today)

tests

• parser test for auth-user-pass (bare and with file path)
• TryFrom test confirming auth_type inference

[cachebag]

Closed in #340