Feature/using encrypted shared preferences

[jimcase]

Continue PR-9 by @tuanbipa.

Description of the Change

The changes focus on introducing modern secure storage practices in Android by using EncryptedSharedPreferences for Android 6.0 (Marshmallow) and above, while maintaining compatibility with older Android versions via the KeyStore system. The solution includes automatic data migration, ensuring a seamless transition without data loss.

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Change List

1. Support for EncryptedSharedPreferences

• New Feature: Utilizes EncryptedSharedPreferences for secure data storage on Android 6.0+.
• Data Migration: Automatically transfers data from legacy SharedPreferences to EncryptedSharedPreferences.

2. Backward Compatibility for Android < 6.0

• Retains the use of the KeyStore system for data encryption and decryption on older Android versions.

3. Introduction of migrationDone Flag

• Purpose: Ensures that data migration happens only once, avoiding unnecessary processing.

4. Helper Method isAndroidMOrHigher

• Purpose: Checks the device's Android version to determine if EncryptedSharedPreferences can be used.

5. Refactored getPrefs Method

• Enhancement:
  • Manages the creation of EncryptedSharedPreferences for Android 6.0+.
  • Handles data migration from legacy SharedPreferences to EncryptedSharedPreferences.
  • Falls back to plain SharedPreferences for Android versions below 6.0.