title: Jenkins DSL : Job SLack publisher : baseUrl() method not available
body: <p>I use Jenkins 2.63 with and Slack Notifier plugin 2.2</p>
  
  <p>I need to generate Jobs with SlackNotifier by Job DSL but  I can not set the Base URL in the DSL, I get this message :</p>
  
  <p>ERROR: (script, line 145) No signature of method: <strong>baseUrl()</strong> is applicable for argument types: (java.lang.String) values: [<a href="https://my.domain.slack.com/services/hooks/jenkins-ci/]" rel="nofollow noreferrer">https://my.domain.slack.com/services/hooks/jenkins-ci/]</a> Possible solutions: authToken(), authTokenCredentialId(), botUser(), commitInfoChoice(), customMessage(), includeCustomMessage(), includeTestSummary(), notifyAborted(), notifyBackToNormal(), notifyFailure(), notifyNotBuilt(), notifyRegression(), notifyRepeatedFailure(), notifySuccess(), notifyUnstable(), room(), sendAs(), startNotification(), teamDomain() Finished: FAILURE</p>
  
  <p>here is my DSL script</p>
  
  <pre><code>        publishers  {
            def slackParam = new groovy.json.JsonSlurper().parse(new File(channelFile))
  
            slackNotifier {
              baseUrl(slackParam.url)
              authTokenCredentialId(slackParam.authTokenCredentialId) 
              includeTestSummary(true) 
              notifyAborted(true) 
              notifyBackToNormal(true) 
              notifyFailure(true) 
              notifyNotBuilt(true) 
              notifyRegression(true) 
              notifyRepeatedFailure(true) 
              notifyUnstable(true)
              room(slackParam.room) 
            }
          }
  </code></pre>
  
  <p>But in the job config.xml I can find this parameter.</p>
  
  <p>Can anyone help me to set the base URL parameter ?</p>
  
  <p>Thanks a lot.</p>