akamai - add api emulator for realistic testing

This simulates the Akamai SIEM API. It provides realistic validation of
request signatures. It emulates the time and offset based queries by
simulating a world in which a new event happens every 5 minutes. The
offset cursor is simply the unix time in sec of the last returned event.

This is a reproducer for the issues described in #9038. Those issues
only occur on Elastic Agent < 8.11.0.

packages/akamai/_dev/deploy/docker/Dockerfile

@@ -0,0 +1,5 @@
+FROM golang:1.21
+
+RUN go install github.com/andrewkroh/go-examples/akamai-siem-simulator@4e9a10a
+
+CMD akamai-siem-simulator -h

packages/akamai/_dev/deploy/docker/docker-compose.yml

@@ -1,14 +1,15 @@
 version: '2.3'
 services:
-  akamai:
-    image: docker.elastic.co/observability/stream:v0.6.1
+  akamai-siem-emulator:
+    hostname: akamai-siem-emulator
+    build:
+      context: .
+      dockerfile: Dockerfile
     ports:
-      - 8080
-    volumes:
-      - ./files:/files:ro
-    environment:
-      PORT: 8080
+      - 9903
     command:
-      - http-server
-      - --addr=:8080
-      - --config=/files/config.yml
+      - akamai-siem-simulator
+      - -http=:9903
+      - -access-token=at-6b8c7217-8748-490d-b0f5-bfeb72b2e7cd
+      - -client-secret=cs-0d15cfd9-764a-48e6-a822-22756180ddb8
+      - -client-token=ct-f625f0b8-9c8f-44ce-8250-eaf17bc93051

packages/akamai/data_stream/siem/_dev/test/system/test-emulator-config.yml

@@ -0,0 +1,16 @@
+input: httpjson
+service: akamai-siem-emulator
+vars: ~
+data_stream:
+  vars:
+    preserve_original_event: true
+    api_host: "http://akamai-siem-emulator:9903"
+    client_token: ct-f625f0b8-9c8f-44ce-8250-eaf17bc93051
+    client_secret: cs-0d15cfd9-764a-48e6-a822-22756180ddb8
+    access_token: at-6b8c7217-8748-490d-b0f5-bfeb72b2e7cd
+    config_ids: 123456
+    event_limit: 20
+    enable_request_tracer: true
+assert:
+  # 24 hours at 5 minutes between events.
+  hit_count: 288 #  = 24 * 60/5