Keep Retrofit interfaces in R8 full mode
Because R8 does not see Proxy as a source of instances, it replaces all potential instances with null
# Top-level functions that can only be used by Kotlin.
-dontwarn retrofit2.-KotlinExtensions
+
+# With R8 full mode, it sees no subtypes of Retrofit interfaces since they are created with a Proxy
+# and replaces all potential values with null. Explicitly keeping the interfaces prevents this.
+-if interface * { @retrofit2.http.* <methods>; }
+-keep,allowobfuscation interface <1>
