Add more sasl LDAP config options

- SASLAUTHD_LDAP_PASSWORD_ATTR => ldap_password_attr
- SASLAUTHD_LDAP_AUTH_METHOD => ldap_auth_method
- SASLAUTHD_LDAP_MECH => ldap_mech

README.md

@@ -854,11 +854,31 @@ File containing CA (Certificate Authority) certificate(s).
 - e.g. for active directory: `(&(sAMAccountName=%U)(objectClass=person))`
 - e.g. for openldap: `(&(uid=%U)(objectClass=person))`
 
+##### SASLAUTHD_LDAP_PASSWORD_ATTR
+
+Specify what password attribute to use for password verification.
+
+- **empty** => Nothing is added to the configuration but the documentation says it is `userPassword` by default.
+- Any value => Fills the `ldap_password_attr` option
+
 ##### SASL_PASSWD
 
 - **empty** => No sasl_passwd will be created
 - string => `/etc/postfix/sasl_passwd` will be created with the string as password
 
+##### SASLAUTHD_LDAP_AUTH_METHOD
+
+- **empty** => `bind` will be used as a default value
+- `fastbind` => The fastbind method is used
+- `custom` => The custom method uses userPassword attribute to verify the password
+
+##### SASLAUTHD_LDAP_MECH
+
+Specify the authentication mechanism for SASL bind.
+
+- **empty** => Nothing is added to the configuration
+- Any value => Fills the `ldap_mech` option
+
 #### SRS (Sender Rewriting Scheme)
 
 ##### SRS_SENDER_CLASSES