add auth plugin

Signed-off-by: Nicola Murino <nicola.murino@gmail.com>

README.md

@@ -67,6 +67,7 @@ If you report an invalid issue or ask for step-by-step support, your issue will
 - Partial authentication. You can configure multi-step authentication requiring, for example, the user password after successful public key authentication.
 - Per-user authentication methods.
 - [Two-factor authentication](./docs/howto/two-factor-authentication.md) based on time-based one time passwords (RFC 6238) which works with Authy, Google Authenticator, Microsoft Authenticator and other compatible apps.
+- LDAP/Active Directory authentication using a [plugin](https://github.com/sftpgo/sftpgo-plugin-auth).
 - Simplified user administrations using [groups](./docs/groups.md).
 - [Roles](./docs/roles.md) allow to create limited administrators who can only create and manage users with their role.
 - Custom authentication via [external programs/HTTP API](./docs/external-auth.md).

docker/scripts/download-plugins.sh

@@ -17,7 +17,7 @@ esac
 
 echo "download plugins for arch ${SUFFIX}"
 
-for PLUGIN in geoipfilter kms pubsub eventstore eventsearch metadata
+for PLUGIN in geoipfilter kms pubsub eventstore eventsearch metadata auth
 do
     echo "download plugin from https://github.com/sftpgo/sftpgo-plugin-${PLUGIN}/releases/latest/download/sftpgo-plugin-${PLUGIN}-linux-${SUFFIX}"
     curl -L "https://github.com/sftpgo/sftpgo-plugin-${PLUGIN}/releases/latest/download/sftpgo-plugin-${PLUGIN}-linux-${SUFFIX}" --output "/usr/local/bin/sftpgo-plugin-${PLUGIN}"