chore: add default to userId in PowerSyncCredentials#22

DominicGBauer merged 1 commit intomainpowersync-ja/powersync-swift:mainfrom

chore/add-default-to-user-id-in-credentialspowersync-ja/powersync-swift:chore/add-default-to-user-id-in-credentialsCopy head branch name to clipboard