server sided external api calls (#697)

* server sided external api calls

* fix uploading gpx files

* rename api/v1/nominatim with api/v1/geocoding to prepare photon support

* remove NOMINATIM_MAX_RETRIES (side-kick from other PR)

* re-add nominatim url fallback

* docu, env var defaults and fallbacks, docker compose files

* refactor

* furhter refactorings and fixes

* PUBLIC_VALHALLA_ENABLED in docker compose files added

* fix env var names

---------

Co-authored-by: Flomp <Flomp@users.noreply.github.com>

web/src/lib/server/overpass.ts

@@ -0,0 +1,34 @@
+import { resolveBaseUrl } from "$lib/server/url";
+import type { RequestEvent } from "@sveltejs/kit";
+
+const OVERPASS_MAX_RETRIES = 2;
+
+function getOverpassBaseUrl(): string {
+    return resolveBaseUrl("OVERPASS_API_URL", "https://overpass-api.de");
+}
+
+export async function fetchOverpass(event: RequestEvent, params: URLSearchParams): Promise<Response> {
+    const baseUrl = getOverpassBaseUrl();
+    const base = new URL(baseUrl.endsWith("/") ? baseUrl : `${baseUrl}/`);
+    const url = new URL("api/interpreter", base);
+    const query = params.toString();
+    if (query.length) {
+        url.search = query;
+    }
+
+    let attempt = 0;
+
+    while (true) {
+        try {
+            return await event.fetch(url.toString(), {
+                method: "GET",
+            });
+        } catch (error) {
+            if (attempt < OVERPASS_MAX_RETRIES) {
+                attempt++;
+                continue;
+            }
+            throw error;
+        }
+    }
+}