Add important proguard rules to keep Netty classes

Issues with those only manifest in release builds with proguard turned on.

This commit also removes some proguard warnings related to Netty.

app/proguard-rules.pro

@@ -21,8 +21,26 @@
 #-renamesourcefileattribute SourceFile
 
 -dontobfuscate
+-keepattributes SourceFile, LineNumberTable, *Annotation*, Signature, InnerClasses, EnclosingMethod
+
 -keep class org.onionshare.android.** { *; }
 -keep class org.torproject.jni.** { *; }
 
--keep class ch.qos.** { *; }
--keep class org.slf4j.** { *; }
+# Keep logging
+-keep public class org.slf4j.** { *; }
+-keep public class ch.qos.logback.** { *; }
+
+# Keep Netty classes that are loaded via reflection
+-keep class io.netty.util.ReferenceCountUtil { *; }
+-keep class io.netty.buffer.WrappedByteBuf { *; }
+
+-dontwarn com.fasterxml.jackson.databind.ext.Java7SupportImpl
+-dontwarn io.netty.internal.tcnative.*
+-dontwarn java.lang.management.*
+-dontwarn org.apache.log4j.*
+-dontwarn org.apache.logging.log4j.**
+-dontwarn org.conscrypt.*
+-dontwarn org.eclipse.jetty.npn.*
+-dontwarn org.jetbrains.annotations.*
+-dontwarn reactor.blockhound.integration.BlockHoundIntegration
+-dontwarn javax.mail.**