add secret: true to hec_token config_param such that it is redacted…

… in the configuration file output (#201)

Signed-off-by: Conor Evans <coevans@tcd.ie>

lib/fluent/plugin/out_splunk_hec.rb

@@ -40,7 +40,7 @@ class SplunkHecOutput < SplunkOutput
     config_param :full_url, :string, default: ''
 
     desc 'The HEC token.'
-    config_param :hec_token, :string
+    config_param :hec_token, :string, secret: true
 
     desc 'If a connection has not been used for this number of seconds it will automatically be reset upon the next use to avoid attempting to send to a closed connection. nil means no timeout.'
     config_param :idle_timeout, :integer, default: 5