mark secret_key in secure_json_data as sensitive (#78)

As it contain sensitive information.

NOTE: currently there is a bug in Terraform, which ignores `Sensitive: true` on fields with type List.

See https://github.com/hashicorp/terraform/issues/15115 for details.

Signed-off-by: Andrei Krasnitski <[email protected]>

Author: Infra-Red

grafana/resource_data_source.go

@@ -107,8 +107,9 @@ func ResourceDataSource() *schema.Resource {
 							Required: true,
 						},
 						"secret_key": {
-							Type:     schema.TypeString,
-							Required: true,
+							Type:      schema.TypeString,
+							Required:  true,
+							Sensitive: true,
 						},
 					},
 				},