Add proguard rules to keep inherited services
-if interface * { @retrofit2.http.* <methods>; }
-keep,allowobfuscation interface <1>
+# Keep inherited services.
+-if interface * { @retrofit2.http.* <methods>; }
+-keep,allowobfuscation interface * extends <1>
+
# Keep generic signature of Call, Response (R8 full mode strips signatures from non-kept items).
-keep,allowobfuscation,allowshrinking interface retrofit2.Call
-keep,allowobfuscation,allowshrinking class retrofit2.Response
