rclone config redacted: implement support mechanism for showing redacted config

This introduces a new fs.Option flag, Sensitive and uses this along
with IsPassword to redact the info in the config file for support
purposes.

It adds this flag into backends where appropriate. It was necessary to
add oauthutil.SharedOptions to some backends as they were missing
them.

Fixes #5209

backend/hdfs/hdfs.go

@@ -19,9 +19,10 @@ func init() {
 		Description: "Hadoop distributed file system",
 		NewFs:       NewFs,
 		Options: []fs.Option{{
-			Name:     "namenode",
-			Help:     "Hadoop name node and port.\n\nE.g. \"namenode:8020\" to connect to host namenode at port 8020.",
-			Required: true,
+			Name:      "namenode",
+			Help:      "Hadoop name node and port.\n\nE.g. \"namenode:8020\" to connect to host namenode at port 8020.",
+			Required:  true,
+			Sensitive: true,
 		}, {
 			Name: "username",
 			Help: "Hadoop user name.",
@@ -29,6 +30,7 @@ func init() {
 				Value: "root",
 				Help:  "Connect to hdfs as root.",
 			}},
+			Sensitive: true,
 		}, {
 			Name: "service_principal_name",
 			Help: `Kerberos service principal name for the namenode.
@@ -36,7 +38,8 @@ func init() {
 Enables KERBEROS authentication. Specifies the Service Principal Name
 (SERVICE/FQDN) for the namenode. E.g. \"hdfs/namenode.hadoop.docker\"
 for namenode running as service 'hdfs' with FQDN 'namenode.hadoop.docker'.`,
-			Advanced: true,
+			Advanced:  true,
+			Sensitive: true,
 		}, {
 			Name: "data_transfer_protection",
 			Help: `Kerberos data transfer protection: authentication|integrity|privacy.