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/path-exists/index.js

@@ -0,0 +1,23 @@
+'use strict';
+const fs = require('fs');
+const {promisify} = require('util');
+
+const pAccess = promisify(fs.access);
+
+module.exports = async path => {
+	try {
+		await pAccess(path);
+		return true;
+	} catch (_) {
+		return false;
+	}
+};
+
+module.exports.sync = path => {
+	try {
+		fs.accessSync(path);
+		return true;
+	} catch (_) {
+		return false;
+	}
+};