This change uses the updated ldap library in minio/pkg (bumped
up to v3). A new config parameter is added for LDAP configuration to
specify extra user attributes to load from the LDAP server and to store
them as additional claims for the user.
A test is added in sts_handlers.go that shows how to access the LDAP
attributes as a claim.
This is in preparation for adding SSH pubkey authentication to MinIO's SFTP
integration.
Following extension allows users to specify immediate purge of
all versions as soon as the latest version of this object has
expired.
```
<LifecycleConfiguration>
<Rule>
<ID>ClassADocRule</ID>
<Filter>
<Prefix>classA/</Prefix>
</Filter>
<Status>Enabled</Status>
<Expiration>
<Days>3650</Days>
<ExpiredObjectAllVersions>true</ExpiredObjectAllVersions>
</Expiration>
</Rule>
...
```
