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-key/index.d.ts

@@ -0,0 +1,40 @@
+/// <reference types="node" />
+
+declare namespace pathKey {
+	interface Options {
+		/**
+		Use a custom environment variables object. Default: [`process.env`](https://nodejs.org/api/process.html#process_process_env).
+		*/
+		readonly env?: {[key: string]: string | undefined};
+
+		/**
+		Get the PATH key for a specific platform. Default: [`process.platform`](https://nodejs.org/api/process.html#process_process_platform).
+		*/
+		readonly platform?: NodeJS.Platform;
+	}
+}
+
+declare const pathKey: {
+	/**
+	Get the [PATH](https://en.wikipedia.org/wiki/PATH_(variable)) environment variable key cross-platform.
+
+	@example
+	```
+	import pathKey = require('path-key');
+
+	const key = pathKey();
+	//=> 'PATH'
+
+	const PATH = process.env[key];
+	//=> '/usr/local/bin:/usr/bin:/bin'
+	```
+	*/
+	(options?: pathKey.Options): string;
+
+	// TODO: Remove this for the next major release, refactor the whole definition to:
+	// declare function pathKey(options?: pathKey.Options): string;
+	// export = pathKey;
+	default: typeof pathKey;
+};
+
+export = pathKey;