Use USER_PASS_LEN instead of TLS_USERNAME_LEN for override-username

Use USER_PASS_LEN instead of TLS_USERNAME_LEN for override-username

Currently override-username is artificially restricted to the length of
TLS common-name (64) for the corner case of using username-as-common-name,
which we explicitly do not recommend to use.

Do away with that limitation and only error out on longer usernames when
username-as-common-name is actually in effect.

Change-Id: I1c2c050dd160746a0f8d9c234abe1e258bc8e48d
Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20250402134546.3504-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg31323.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>