Update DEVELOPER.md

Updates DEVELOPER.md instructions with the OSM OAuth2 Application Permissions and Redirect URIs. Adds needed clarity for developers to make sure the app has the required permissions if compiling on their own.

DEVELOPER.md

@@ -854,6 +854,13 @@ To run the app with working OSM authentication, register OAuth2 applications:
 
 1. **Production OSM**: https://www.openstreetmap.org/oauth2/applications
 2. **Sandbox OSM**: https://master.apis.dev.openstreetmap.org/oauth2/applications
+3. **OAuth2 Application Permissions**
+   * Uncheck "Confidential application?"
+   * Read user preferences (read_prefs)
+   * Modify the map (write_api)
+   * Read, update status and delete user messages (consume_messages)
+4. **Redirect URIs**
+   * deflockapp://auth
 
 For local builds, create `build_keys.conf` (gitignored):
 ```bash