feat: Adds automatic thread scaling at runtime and php_ini configuration in Caddyfile (#1266)

Adds option to scale threads at runtime

Adds php_ini configuration in Caddyfile

testdata/performance/api.js

@@ -0,0 +1,29 @@
+import http from 'k6/http'
+
+/**
+ * Many applications communicate with external APIs or microservices.
+ * Latencies tend to be much higher than with databases in these cases.
+ * We'll consider 10ms-150ms
+ */
+export const options = {
+  stages: [
+    { duration: '20s', target: 150 },
+    { duration: '20s', target: 1000 },
+    { duration: '10s', target: 0 }
+  ],
+  thresholds: {
+    http_req_failed: ['rate<0.01']
+  }
+}
+
+/* global __ENV */
+export default function () {
+  // 10-150ms latency
+  const latency = Math.floor(Math.random() * 141) + 10
+  // 1-30000 work units
+  const work = Math.ceil(Math.random() * 30000)
+  // 1-40 output units
+  const output = Math.ceil(Math.random() * 40)
+
+  http.get(http.url`${__ENV.CADDY_HOSTNAME}/sleep.php?sleep=${latency}&work=${work}&output=${output}`)
+}