[Issue 10169] Add support for token only authentication with otp overlay

https://bugs.openldap.org/show_bug.cgi?id=10169

--- Comment #3 from Bastian Tweddell bastian-bugopenldap21@t6l.de --- We are still using contrib/pw-totp. And today it bit us again with:

``` slapd[2970]: Entry (...,ou=jsc,dc=fz-juelich,dc=de), attribute 'authTimestamp' cannot have multiple values slapd[2970]: entry failed schema check: attribute 'authTimestamp' cannot have multiple values slapd[2970]: conn=6302 op=0 RESULT tag=97 err=49 qtime=0.000007 etime=0.000330 text= ```

This DB is a replica which will be re-synched from scratch to get rid of those extra attributes.

I'd like to ask again if it would be deemed possible at all to implement an OTP-only authentication for bind with the slapo-otp overlay? TIA