fix(server): opus handling as accepted audio codec in transcode policy (#26736)

* Fix opus handling as accepted audio codec in transcode policy

Fix the issue when opus is among accepted audio codecs in transcode policy
(which is default) but it still triggers transcoding because the codec name
from ffprobe (opus) does not match `libopus` literal in Immich.

Make a distinction between a codec name and encoder:
- codec name: switch to `opus` as the audio codec name. This matches what ffprobe
returns for a media file with opus audio.
- encoder: continue using the `libopus` encoder in ffmpeg.

* Add unit tests for accepted audio codecs and for libopus encoder

* Add db migration for ffmpeg.targetAudioCodec opus

* backward compatibility

* tweak

* noisy logs

* full mapping

* make check happy

* mark deprecated

* update api

* indexOf

---------

Co-authored-by: mertalev <101130780+mertalev@users.noreply.github.com>

docs/docs/administration/system-settings.md

@@ -230,7 +230,7 @@ The default value is `ultrafast`.
 
 ### Audio codec (`ffmpeg.targetAudioCodec`) {#ffmpeg.targetAudioCodec}
 
-Which audio codec to use when the audio stream is being transcoded. Can be one of `mp3`, `aac`, `libopus`.
+Which audio codec to use when the audio stream is being transcoded. Can be one of `mp3`, `aac`, `opus`.
 
 The default value is `aac`.
 

docs/docs/install/config-file.md

@@ -27,7 +27,7 @@ The default configuration looks like this:
   "ffmpeg": {
     "accel": "disabled",
     "accelDecode": false,
-    "acceptedAudioCodecs": ["aac", "mp3", "libopus"],
+    "acceptedAudioCodecs": ["aac", "mp3", "opus"],
     "acceptedContainers": ["mov", "ogg", "webm"],
     "acceptedVideoCodecs": ["h264"],
     "bframes": -1,