Prevent empty LDAP search from deactivating all users (#9879) (#9890)

* Backport of #9879 (Add option to prevent LDAP from deactivating everything on empty search)

* go fmtted

Co-authored-by: Antoine GIRARD <sapk@users.noreply.github.com>
Co-authored-by: zeripath <art27@cantab.net>

cmd/admin_auth_ldap.go

@@ -61,6 +61,10 @@ var (
 			Name:  "admin-filter",
 			Usage: "An LDAP filter specifying if a user should be given administrator privileges.",
 		},
+		cli.BoolFlag{
+			Name:  "allow-deactivate-all",
+			Usage: "Allow empty search results to deactivate all users.",
+		},
 		cli.StringFlag{
 			Name:  "username-attribute",
 			Usage: "The attribute of the user’s LDAP record containing the user name.",
@@ -231,6 +235,9 @@ func parseLdapConfig(c *cli.Context, config *models.LDAPConfig) error {
 	if c.IsSet("admin-filter") {
 		config.Source.AdminFilter = c.String("admin-filter")
 	}
+	if c.IsSet("allow-deactivate-all") {
+		config.Source.AllowDeactivateAll = c.Bool("allow-deactivate-all")
+	}
 	return nil
 }