Watcher: migrate PagerDuty v1 events API to v2 API

The PagerDuty v1 API is EOL and will stop accepting new accounts
shortly. This commit swaps out the watcher use of the v1 API with the
new v2 API. It does not change anything about the existing watcher
API.

Closes elastic#32243

x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/notification/pagerduty/IncidentEvent.java

@@ -39,7 +39,8 @@
 public class IncidentEvent implements ToXContentObject {
 
     static final String HOST = "events.pagerduty.com";
-    static final String PATH = "/generic/2010-04-15/create_event.json";
+    static final String PATH = "/v2/enqueue";
+    static final String ACCEPT_HEADER = "application/vnd.pagerduty+json;version=2";
 
     final String description;
     @Nullable final HttpProxy proxy;
@@ -99,40 +100,85 @@ public HttpRequest createRequest(final String serviceKey, final Payload payload)
                 .scheme(Scheme.HTTPS)
                 .path(PATH)
                 .proxy(proxy)
+                .setHeader("Accept", ACCEPT_HEADER)
                 .jsonBody(new ToXContent() {
                     @Override
                     public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
-                        builder.field(Fields.SERVICE_KEY.getPreferredName(), serviceKey);
-                        builder.field(Fields.EVENT_TYPE.getPreferredName(), eventType);
-                        builder.field(Fields.DESCRIPTION.getPreferredName(), description);
+                        builder.field("routing_key", serviceKey);
+                        builder.field("event_action", eventType);
                         if (incidentKey != null) {
-                            builder.field(Fields.INCIDENT_KEY.getPreferredName(), incidentKey);
+                            builder.field("dedup_key", incidentKey);
                         }
+
+                        builder.startObject("payload");
+                        {
+                            builder.field("summary", description);
+
+                            if (attachPayload) {
+                                builder.startObject("custom_details");
+                                builder.field(Fields.PAYLOAD.getPreferredName());
+                                payload.toXContent(builder, params);
+                                builder.endObject();
+                            }
+
+                            // TODO externalize this into something user editable
+                            builder.field("source", "watcher");
+                            builder.field("severity", "critical");
+                        }
+                        builder.endObject();
+
                         if (client != null) {
                             builder.field(Fields.CLIENT.getPreferredName(), client);
                         }
                         if (clientUrl != null) {
                             builder.field(Fields.CLIENT_URL.getPreferredName(), clientUrl);
                         }
-                        if (attachPayload) {
-                            builder.startObject(Fields.DETAILS.getPreferredName());
-                            builder.field(Fields.PAYLOAD.getPreferredName());
-                            payload.toXContent(builder, params);
-                            builder.endObject();
-                        }
+
                         if (contexts != null && contexts.length > 0) {
-                            builder.startArray(Fields.CONTEXTS.getPreferredName());
-                            for (IncidentEventContext context : contexts) {
-                                context.toXContent(builder, params);
-                            }
-                            builder.endArray();
+                            toXContentV2Contexts(builder, params, contexts);
                         }
+
                         return builder;
                     }
                 })
                 .build();
     }
 
+    /**
+     * Turns the V1 API contexts into 2 distinct lists, images and links. The V2 API has separated these out into 2 top level fields.
+     */
+    private void toXContentV2Contexts(XContentBuilder builder, ToXContent.Params params,
+                                      IncidentEventContext[] contexts) throws IOException {
+        // contexts can be either links or images, and the v2 api needs them separate
+        List<IncidentEventContext> links = new ArrayList<>();
+        List<IncidentEventContext> images = new ArrayList<>();
+        for (IncidentEventContext context: contexts) {
+            if (context.type == IncidentEventContext.Type.LINK) {
+                links.add(context);
+            } else if (context.type == IncidentEventContext.Type.IMAGE) {
+                images.add(context);
+            }
+        }
+        if (links.isEmpty() == false) {
+            builder.startArray("links");
+            {
+                for (IncidentEventContext link: links) {
+                    link.toXContent(builder, params);
+                }
+            }
+            builder.endArray();
+        }
+        if (images.isEmpty() == false) {
+            builder.startArray("images");
+            {
+                for (IncidentEventContext image: images) {
+                    image.toXContent(builder, params);
+                }
+            }
+            builder.endArray();
+        }
+    }
+
     @Override
     public XContentBuilder toXContent(XContentBuilder builder, ToXContent.Params params) throws IOException {
         builder.startObject();