Print the job's groupname if present

We have several groups containing jobs with equal names, e.g.

group1:
  - update
  - restart
group2:
  - update
  - restart

In Slack we can now differentiate between the jobs: "Execution #246 of group1/update"
instead of just: "Execution #246 of update"

src/main/resources/templates/slack-incoming-message.ftl

@@ -1,11 +1,17 @@
-<#assign message="<${executionData.href}|Execution #${executionData.id}> of job <${executionData.job.href}|${executionData.job.name}>">
+<#if executionData.job.group??>
+    <#assign jobName="${executionData.job.group} / ${executionData.job.name}">
+<#else>
+    <#assign jobName="${executionData.job.name}">
+</#if>
+<#assign message="<${executionData.href}|Execution #${executionData.id}> of job <${executionData.job.href}|${jobName}>">
 <#if trigger == "start">
     <#assign state="Started">
 <#elseif trigger == "failure">
     <#assign state="Failed">
 <#else>
     <#assign state="Succeeded">
 </#if>
+
 {
    "attachments":[
       {
@@ -15,7 +21,7 @@
          "fields":[
             {
                "title":"Job Name",
-               "value":"<${executionData.job.href}|${executionData.job.name}>",
+               "value":"<${executionData.job.href}|${jobName}>",
                "short":true
             },
             {