dev-api: add developer portal, OpenAPI spec, and Flatenbadet case study

- New /developers/ page with API docs, SDKs, pricing, use cases
- OpenAPI 3.0 spec for Orders, Missions, Photos, Analytics
- Case study: Glasskiosken i Flatenbadet — complete ROI analysis
- Updated /order/ with recurring missions and frequency dropdown

services/frilans-payout/node_modules/reusify/reusify.js

@@ -0,0 +1,33 @@
+'use strict'
+
+function reusify (Constructor) {
+  var head = new Constructor()
+  var tail = head
+
+  function get () {
+    var current = head
+
+    if (current.next) {
+      head = current.next
+    } else {
+      head = new Constructor()
+      tail = head
+    }
+
+    current.next = null
+
+    return current
+  }
+
+  function release (obj) {
+    tail.next = obj
+    tail = obj
+  }
+
+  return {
+    get: get,
+    release: release
+  }
+}
+
+module.exports = reusify