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/eslint/messages/failed-to-read-json.js

@@ -0,0 +1,11 @@
+"use strict";
+
+module.exports = function(it) {
+    const { path, message } = it;
+
+    return `
+Failed to read JSON file at ${path}:
+
+${message}
+`.trimStart();
+};