Encrypt LDAP bind password in db with SECRET_KEY (#15547)

* Encrypt LDAP bind password in db with SECRET_KEY

The LDAP source bind password are currently stored in plaintext in the db
This PR simply encrypts them with the setting.SECRET_KEY.

Fix #15460

Signed-off-by: Andrew Thornton <art27@cantab.net>

* remove ui warning regarding unencrypted password

Co-authored-by: silverwind <me@silverwind.io>

modules/auth/ldap/ldap.go

@@ -35,6 +35,7 @@ type Source struct {
 	SecurityProtocol      SecurityProtocol
 	SkipVerify            bool
 	BindDN                string // DN to bind with
+	BindPasswordEncrypt   string // Encrypted Bind BN password
 	BindPassword          string // Bind DN password
 	UserBase              string // Base search path for users
 	UserDN                string // Template for the DN of the user for simple auth