Add Javadoc documentation to mapCryptoExceptionToErrorCode helper method

[Copilot]

Addresses missing documentation for the mapCryptoExceptionToErrorCode helper method introduced in PR #2844, as noted in review comment #2641260485.

Changes

• Added comprehensive Javadoc to mapCryptoExceptionToErrorCode documenting:
  • Purpose: maps cryptographic exceptions to ClientException error code constants
  • Parameter: the exception to map (non-null)
  • Return value: corresponding error code constant with INVALID_KEY as default fallback
  • Usage context: shared by both encrypt and decrypt operations for consistent error mapping

/**
 * Maps cryptographic exceptions to corresponding ClientException error code constants.
 * This helper method is used by both encrypt and decrypt operations to provide consistent
 * error code mappings for various cryptographic failure scenarios.
 *
 * @param e The exception to map to an error code. Must be non-null.
 * @return The corresponding ClientException error code constant. Returns {@link ClientException#INVALID_KEY}
 *         as the default fallback when the exception type doesn't match any known types.
 */
private String mapCryptoExceptionToErrorCode(@NonNull final Exception e) { ... }

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