Watcher: Jira fields do not use template rendering for every field

[elasticmachine]

Original comment by @spinscale:

The following example jira configuration will result in no changes in the components array due to the current implementation, regular string fields are correctly replaced

    "actions": {
      "create-jira-issue": {
        "jira": {
          "account": "monitoring",
          "fields": {
            "summary": "correctly replaced {{ctx.payload}}",
            "issuetype": {
              "name": "Alert"
            },
            "components": [
              {
                "name": "not replaced {{ctx.payload}}"
              }
            ],
            "project": {
              "key": "MMA"
            },
            "customfield_10200": 2
          }
        }
      }
    }
  }

The reason for this is the broken ExecutableJiraAction.merge method, because it does not do the right thing when a list, that is not comprised of a string value is found - which for a map is simple to add.

This unit test resembles the broken behaviour and fails on the last assert

    public void testMerge() {
        Map<String, Object> writeableMap = new HashMap<>();
        Map<String, Object> map = new HashMap<>();
        map.put("foo", "bar");
        Map<String, Object> componentMap = new HashMap<>();
        componentMap.put("name", "value");
        List<Map<String, Object>> list = new ArrayList<>();
        list.add(componentMap);
        map.put("components", list);
        Map<String, Object> result = ExecutableJiraAction.merge(writeableMap, map, s -> s.toUpperCase(Locale.ROOT));
        assertThat(result, hasEntry("FOO", "BAR"));
        assertThat(result.get("COMPONENTS"), instanceOf(List.class));
        List<Map<String, Object>> components = (List<Map<String, Object>>) result.get("COMPONENTS");
        assertThat(components.get(0), hasEntry("NAME", "VALUE"));
    }

[elasticmachine]

Original comment by @spinscale:

this is a preliminary fix, but the full PR should also contain proper unit testing for the merge method itself, as it is untested it seems

--- a/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/actions/jira/ExecutableJiraAction.java
+++ b/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/actions/jira/ExecutableJiraAction.java
@@ -100,6 +100,8 @@ public class ExecutableJiraAction extends ExecutableAction<JiraAction> {
                     for (Object v : (List) value) {
                         if (v instanceof String) {
                             newValues.add(fn.apply((String) v));
+                        } else if (v instanceof Map) {
+                            newValues.add(merge(new HashMap<>(), (Map<String, ?>) v, fn));
                         } else {
                             newValues.add(v);
                         }