refactor(server): modularize getFfmpegOptions (#3138)

* refactored `getFfmpegOptions`

refactor transcoding, make separate service

* fixed enum casing

* use `Logger` instead of `console.log`

* review suggestions

* use enum for `getHandler`

* fixed formatting

* Update server/src/domain/media/media.util.ts

Co-authored-by: Jason Rasmussen <jrasm91@gmail.com>

* Update server/src/domain/media/media.util.ts

Co-authored-by: Jason Rasmussen <jrasm91@gmail.com>

* More specific imports, renamed codec classes

* simplified code

* removed unused import

* added tests

* added base implementation for bitrate and threads

---------

Co-authored-by: Jason Rasmussen <jrasm91@gmail.com>

mobile/openapi/lib/model/audio_codec.dart

@@ -0,0 +1,88 @@
+//
+// AUTO-GENERATED FILE, DO NOT MODIFY!
+//
+// @dart=2.12
+
+// ignore_for_file: unused_element, unused_import
+// ignore_for_file: always_put_required_named_parameters_first
+// ignore_for_file: constant_identifier_names
+// ignore_for_file: lines_longer_than_80_chars
+
+part of openapi.api;
+
+
+class AudioCodec {
+  /// Instantiate a new enum with the provided [value].
+  const AudioCodec._(this.value);
+
+  /// The underlying value of this enum member.
+  final String value;
+
+  @override
+  String toString() => value;
+
+  String toJson() => value;
+
+  static const mp3 = AudioCodec._(r'mp3');
+  static const aac = AudioCodec._(r'aac');
+  static const opus = AudioCodec._(r'opus');
+
+  /// List of all possible values in this [enum][AudioCodec].
+  static const values = <AudioCodec>[
+    mp3,
+    aac,
+    opus,
+  ];
+
+  static AudioCodec? fromJson(dynamic value) => AudioCodecTypeTransformer().decode(value);
+
+  static List<AudioCodec>? listFromJson(dynamic json, {bool growable = false,}) {
+    final result = <AudioCodec>[];
+    if (json is List && json.isNotEmpty) {
+      for (final row in json) {
+        final value = AudioCodec.fromJson(row);
+        if (value != null) {
+          result.add(value);
+        }
+      }
+    }
+    return result.toList(growable: growable);
+  }
+}
+
+/// Transformation class that can [encode] an instance of [AudioCodec] to String,
+/// and [decode] dynamic data back to [AudioCodec].
+class AudioCodecTypeTransformer {
+  factory AudioCodecTypeTransformer() => _instance ??= const AudioCodecTypeTransformer._();
+
+  const AudioCodecTypeTransformer._();
+
+  String encode(AudioCodec data) => data.value;
+
+  /// Decodes a [dynamic value][data] to a AudioCodec.
+  ///
+  /// If [allowNull] is true and the [dynamic value][data] cannot be decoded successfully,
+  /// then null is returned. However, if [allowNull] is false and the [dynamic value][data]
+  /// cannot be decoded successfully, then an [UnimplementedError] is thrown.
+  ///
+  /// The [allowNull] is very handy when an API changes and a new enum value is added or removed,
+  /// and users are still using an old app with the old code.
+  AudioCodec? decode(dynamic data, {bool allowNull = true}) {
+    if (data != null) {
+      switch (data) {
+        case r'mp3': return AudioCodec.mp3;
+        case r'aac': return AudioCodec.aac;
+        case r'opus': return AudioCodec.opus;
+        default:
+          if (!allowNull) {
+            throw ArgumentError('Unknown enum value to decode: $data');
+          }
+      }
+    }
+    return null;
+  }
+
+  /// Singleton [AudioCodecTypeTransformer] instance.
+  static AudioCodecTypeTransformer? _instance;
+}
+