Replace UPDATE with UPSERT

[NCura]

Possible fix for issue 36.

This PR replaces the use of UPDATE with UPSERT. According to the SurrealQL documentation, UPSERT ensures that records are created if they don't already exist, addressing the issue where sessions were not being properly saved.

UPDATE on a single record in SurrealDB 1.x will create the record if it does not exist. This behaviour is no longer the case in SurrealDB 2.0. To update and create a record if it does not exist in SurrealDB 2.0, use the UPSERT statement.

[genusistimelord]

thank you. Yeah I did not know they made that change.