enable youtube oauth for login-gated tracks

lavalink/application.yml

@@ -27,13 +27,30 @@ plugins:
   youtube:
     enabled: true
     allowSearch: true     # enables the "ytsearch:" queries the bot falls back to
+    # Tried in order; the first one that can load the track wins. TV is last
+    # because it needs a signed-in account (see oauth below), but it's the only
+    # client that plays age-restricted / "sign in to confirm you're not a bot"
+    # tracks, so it's the fallback when the others get rejected.
     clients:
       - MUSIC
       - WEB
       - WEBEMBEDDED
       - ANDROID_VR
+      - TV
+    oauth:
+      # Links a Google account to the TV client. On first start with no refresh
+      # token, Lavalink logs a google.com/device code — open it, enter the code,
+      # and the plugin then logs a refresh token. Put that token in .env as
+      # PLUGINS_YOUTUBE_OAUTH_REFRESHTOKEN (docker-compose already passes .env
+      # into the Lavalink container, and Spring binds that name onto this key)
+      # so the device flow is skipped on every later start.
+      #
+      # Use a throwaway Google account. Google does ban accounts for this.
+      enabled: true
 
 logging:
   level:
     root: INFO
     lavalink: INFO
+    # Prints the device code and, after you authorize, the refresh token.
+    dev.lavalink.youtube.http.YoutubeOauth2Handler: INFO