chore: update ProGuard rules

- Keep necessary classes for Optimizely and Jackson libraries
- Keep Logback classes
- Remove unnecessary warnings for javax.mail classes
- Add ProGuard configuration to build.gradle for minification
- Update proguard-rules.txt in app folder

Author: muzahidul-opti

android/proguard-rules.txt

@@ -13,9 +13,4 @@
 # Logback
 -keep class ch.qos.** { *; }
 
-# Mail classes (Logback SMTP appender)
--dontwarn javax.mail.**
--dontwarn javax.mail.internet.**
--dontwarn javax.activation.**
-
 ##---------------End: proguard configuration ----------

example/android/app/build.gradle

@@ -49,6 +49,8 @@ android {
         release {
             // TODO: Add your own signing config for the release build.
             // Signing with the debug keys for now, so `flutter run --release` works.
+            minifyEnabled true
+            proguardFiles 'proguard-rules.txt'
             signingConfig signingConfigs.debug
         }
     }

example/android/app/proguard-rules.txt

@@ -0,0 +1,4 @@
+# Mail classes (Logback SMTP appender)
+-dontwarn javax.mail.**
+-dontwarn javax.mail.internet.**
+-dontwarn javax.activation.**