Split derp into its own config struct

config.yaml.sqlite.example

@@ -1,26 +1,43 @@
 ---
+log_level: info
 server_url: http://127.0.0.1:8080
 listen_addr: 0.0.0.0:8080
 private_key_path: private.key
-derp_map_path: derp.yaml
 ephemeral_node_inactivity_timeout: 30m
 
 # SQLite config (uncomment it if you want to use SQLite)
 db_type: sqlite3
 db_path: db.sqlite
 
+derp:
+  # List of externally available DERP maps encoded in JSON
+  urls:
+    - https://controlplane.tailscale.com/derpmap/default
+
+  # Locally available DERP map files encoded in YAML
+  paths:
+    - derp-example.yaml
+
+  # If enabled, a worker will be set up to periodically
+  # refresh the given sources and update the derpmap
+  # will be set up.
+  auto_update_enabled: true
+
+  # How often should we check for updates?
+  update_frequency: 24h
+
 acme_url: https://acme-v02.api.letsencrypt.org/directory
-acme_email: ''
-tls_letsencrypt_hostname: ''
+acme_email: ""
+tls_letsencrypt_hostname: ""
 tls_letsencrypt_listen: ":http"
 tls_letsencrypt_cache_dir: ".cache"
 tls_letsencrypt_challenge_type: HTTP-01
-tls_cert_path: ''
-tls_key_path: ''
-acl_policy_path: ''
+tls_cert_path: ""
+tls_key_path: ""
+acl_policy_path: ""
 dns_config:
   nameservers:
-  - 1.1.1.1
+    - 1.1.1.1
   domains: []
   magic_dns: true
   base_domain: example.com