Add README to document configuration

See merge request !2

Previously, users imported from LDAP had no verified mail address causing
many problems with Postorius and Hyperkitty.

Also prevents users from changing their username, first name or last name.

Fixes #3

LDAP errors were previously misinterpreted as an empty set of results, causing
mass-unsubscription of list members.

Fixes #1

set user mail adress to verified if it matches the one in ldap

See merge request !1

fixup! handle multiple mail addresses and cancle any subscription requests for addresses we try to subscribe

handle multiple mail addresses and cancle any subscription requests for addresses we try to subscribe