Loads a group session from a pickled base64 string. Decrypts the session
using the supplied key.
Returns olm_error() on failure. If the key doesn't match the one used to
encrypt the account then olm_outbound_group_session_last_error() will be
"BAD_ACCOUNT_KEY". If the base64 couldn't be decoded then
olm_outbound_group_session_last_error() will be "INVALID_BASE64". The input
pickled buffer is destroyed
Loads a group session from a pickled base64 string. Decrypts the session using the supplied key.
Returns olm_error() on failure. If the key doesn't match the one used to encrypt the account then olm_outbound_group_session_last_error() will be "BAD_ACCOUNT_KEY". If the base64 couldn't be decoded then olm_outbound_group_session_last_error() will be "INVALID_BASE64". The input pickled buffer is destroyed