geolocation api rate-limit: add per-provider prefix to cached response, refactor geocoding provider code

server/services/geocoding/photon.js

@@ -0,0 +1,18 @@
+
+module.exports = {
+  commonName: 'Photon',
+  DEFAULT_ENDPOINT: 'https://photon.komoot.io/api/',
+  endpoint: (req, res) => {
+    return res.locals.settings.geocoding_provider || this.DEFAULT_ENDPOINT
+  },
+
+  getParams (req, res) {
+    const details = req.params.place_details
+
+    return {
+      q: details,
+      limit: 3,
+    }
+  }
+
+}