Transcoding at lower bitrate for limited bandwidth (#58)

Hello!

To begin with, thanks a lot for Funkwhale and the Android application, which is delightful to use every day.

As mentioned in #58, the application does not yet have a way to reduce the amount of data exchanged between the player and the server. When streaming high-quality audio on 4G or 5G connection, it can get very costly if one does consume a lot of FLAC content. This PR is an attempt at solving this issue and is my first contribution to the project. I would appreciate some hints/helps according to unit tests, translations, and probably things I did not cover for the moment...

Here is a summary of what I have done:

• Add a new setting called "Bandwidth limitation" with an icon, and a basic description,
• If bandwidth limitation is set to limited, append &to=mp3&max_bitrate=320 to the listen URL of the candidate best track upload.

A better way to do it in the future would be to add a bar to configure the desired maximum bitrate, and probably check in the cache if the best upload is already there before asking for a reduced one. Testing that the best quality upload is already meeting the bandwidth constraint would be interesting to avoid an unneeded transcoding on the server side. I prefer to point out the flaws so that we can discuss about them together! 😄

Thank in advance,

Dylan

app/src/main/java/audio/funkwhale/ffa/activities/SettingsActivity.kt

@@ -114,6 +114,14 @@ class SettingsFragment :
         }
       }
 
+      preferenceManager.findPreference<ListPreference>("bandwidth_limitation")?.let {
+        it.summary = when (it.value) {
+          "unlimited" -> activity.getString(R.string.settings_bandwidth_limitation_summary_unlimited)
+          "limited" -> activity.getString(R.string.settings_bandwidth_limitation_summary_limited)
+          else -> activity.getString(R.string.settings_bandwidth_limitation_summary_unlimited)
+        }
+      }
+
       preferenceManager.findPreference<ListPreference>("play_order")?.let {
         it.summary = when (it.value) {
           "shuffle" -> activity.getString(R.string.settings_play_order_shuffle_summary)