Add proguard rules for fyyd client (retrofit & moshi)

app/proguard.cfg

@@ -107,4 +107,19 @@
 -dontwarn com.viewpagerindicator.LinePageIndicator
 
 # for some reason ProGuard removes this file. Why? Unsure.
--keep class de.danoeh.antennapod.core.cast.SwitchableMediaRouteActionProvider { *; }
+-keep class de.danoeh.antennapod.core.cast.SwitchableMediaRouteActionProvider { *; }
+
+# Retrofit 2.0
+-dontwarn retrofit2.**
+-keep class retrofit2.** { *; }
+-keepattributes Signature
+-keepattributes Exceptions
+
+-keepclasseswithmembers class * {
+    @retrofit2.http.* <methods>;
+}
+
+# Moshi
+-keep class com.squareup.moshi.** { *; }
+-keep interface com.squareup.moshi.** { *; }
+-keep public class retrofit2.adapter.rxjava.RxJavaCallAdapterFactory { *; }