RUBY-3620 - Sessions should ignore "cluster mismatched" validation and execute commands on other clusters #2918
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As per RUBY-3620, when using a Session transaction, currently, it is impossible to execute any command on any other cluster. This is a big problem if you have model callbacks which are cross-cluster--your app fails and there's nothing you can do about it 🤦♂️
At a minimum, it is better to allow cross-cluster commands to execute within transactions, i.e. on a separate session for that cluster.
In the future (not in this PR), we could allow:
Note that this PR introduces/extracts out SessionClusterMismatched error (base class SessionInvalid)