Alerting: Add value to notifier template (#41951)

* add value to email template

* add value to default template

* update test string

* test: fix ngalert test suite

* test: run CI

Co-authored-by: gillesdemey <gilles.de.mey@gmail.com>

emails/templates/ng_alert_notification.html

@@ -1,6 +1,11 @@
 [[Subject .Subject "[[.Title]]"]]
 
 [[ define "alert" ]]
+<tr>
+  <td colspan="2" class="value">
+    <span class="value-heading">Value:</span> <span class="value-value">[[ .ValueString ]]</span>
+  </td>
+</tr>
   [[ if gt (len .Annotations.SortedPairs) 0 ]]
       <tr>
         <td colspan="2" class="annotations">
@@ -108,6 +113,16 @@
     margin: 0 10px 0 0;
     padding: 5px 9px;
   }
+  .value {
+    font-size: 14px;
+    padding-top: 24px;
+  }
+  .value-heading {
+    font-weight: bold;
+  }
+  .value-value {
+    padding-left: 8px;
+  }
   .annotations {
     font-size: 14px;
     padding: 24px 0 12px 0;