Rewrite AutocryptHeader and AutocryptGossipHeader in Kotlin instead of Java

[shamim-emon]

• Fixes Rewrite AutocryptHeader and AutocryptGossipHeader in Kotlin instead of Java #9758
• Summary : This PR refactors the existing AutocryptHeader and AutocryptGossipHeader classes from Java into idiomatic Kotlin. The conversion simplifies code, enhances null safety, and leverages Kotlin’s modern language features.
• Implementation Highlights:
  • AutocryptHeader.kt:
    • Rewritten as a Kotlin class with primary constructor parameters:
      • parameters: Map<String, String>
      • addr: String
      • keyData: ByteArray
      • isPreferEncryptMutual: Boolean
    • toRawHeaderString() method builds the header string with support for folding base64 key data.
    • Overridden equals() and hashCode() methods based on Kotlin's conventions.
    • Companion object defines constants such as AUTOCRYPT_HEADER, AUTOCRYPT_PARAM_ADDR, and a helper createFoldedBase64KeyData() method for formatting
  • AutocryptGossipHeader.kt :
    • Defined as an internal data class:
      • Fields: addr: String, keyData: ByteArray
      • toRawHeaderString() method similar to AutocryptHeader
      • equals() and hashCode() override using contentEquals() and contentHashCode() for byte arrays
      • Companion object includes constants: AUTOCRYPT_GOSSIP_HEADER, AUTOCRYPT_PARAM_ADDR, AUTOCRYPT_PARAM_KEY_DATA
  • Updated references in codebase:
    • Minor adjustments in AutocryptOperations.java to accommodate Kotlin properties instead of Java getters: moved from autocryptHeader.getKeyData() to Kotlin-style property access autocryptHeader.keyData, and similarly for other fields
  • Test updates: Refactored AutocryptHeaderParserTest.java to reflect Kotlin property access instead of Java getter methods, ensuring test compatibility:
    • Replaced autocryptHeader.getAddr(), .getKeyData(), .getParameters() with Kotlin property access autocryptHeader.addr, .keyData, .parameters
    • Adjusted input stream handling for test resource loading (readFromResourceFile) to account for simpler method signature

[rafaeltonholo]

Thanks for this contribution, there is just one point to address (spread operator) before merging this.

[rafaeltonholo]

LGTM