message: Add basic methods for new agent2agent approach in signus header.
diff: @@ -129,6 +129,63 @@ extern "C" {
  indy_error_t err)
  );
  + extern indy_error_t indy_create_key(indy_handle_t command_handle,
  + const char *const seed,
  +
  + void (*cb)(indy_handle_t command_handle,
  + indy_error_t err
  + const char *const vk)
  + );
  +
  + extern indy_error_t indy_store_key_meta(indy_handle_t command_handle
  + const char *const vk,
  + const char *const meta,
  +
  + void (*cb)(indy_handle_t command_handle,
  + indy_error_t err)
  + );
  +
  + extern indy_error_t indy_get_key_meta(indy_handle_t command_handle
  + const char *const vk,
  +
  + void (*cb)(indy_handle_t command_handle,
  + indy_error_t err,
  + const char *const meta)
  + );
  +
  + extern indy_error_t indy_key_for_did(indy_handle_t command_handle
  + const char *const did,
  +
  + void (*cb)(indy_handle_t command_handle,
  + indy_error_t err,
  + const char *const key)
  + );
  +
  + extern indy_error_t indy_endpoint_for_did(indy_handle_t command_handle
  + const char *const did,
  +
  + void (*cb)(indy_handle_t command_handle,
  + indy_error_t err,
  + const char *const endpoint,
  + const char *const transport_vk)
  + );
  +
  + extern indy_error_t indy_store_did_meta(indy_handle_t command_handle
  + const char *const did,
  + const char *const meta,
  +
  + void (*cb)(indy_handle_t command_handle,
  + indy_error_t err)
  + );
  +
  + extern indy_error_t indy_get_did_meta(indy_handle_t command_handle
  + const char *const did,
  +
  + void (*cb)(indy_handle_t command_handle,
  + indy_error_t err,
  + const char *const meta)
  + );
  +
  /// Signs a message by a signing key associated with my DID. The DID with a signing key
  /// must be already created and stored in a secured wallet (see create_and_store_my_identity)
  ///
  @@ -353,6 +410,15 @@ extern "C" {
  indy_u32_t decrypted_msg_len)
  );
  +/* TODO implement for key-based approach:
  + indy_sign(signer_vk, msg) -> signature
  + indy_verify(signer_vk, msg, signature) -> bool
  + indy_encrypt(sender_vk, recepient_vk, msg) -> (nonce, encrypted_msg)
  + indy_decrypt(sender_vk, recepient_vk, encrypted_msg, nonce) -> msg
  + indy_encrypt_anonymous(recepient_vk, msg) -> encrypted_msg
  + indy_decrypt_anonymous(recepient_vk, encrypted_msg) -> msg
  +*/
  +
  #ifdef __cplusplus
  }
  #endif
  