Sql: Should not be able to update the PK from GraphQL

The update GraphQL mutations allow ability to modify a PK even if its autogenerated. This should not be allowed.

Start at the GraphQL update mutation entry points and trace how autogenerated primary keys are handled. Confirm completion by ensuring update mutations reject changes to autogenerated primary keys while preserving valid updates to other fields, and add or run the relevant mutation coverage if available.

Written by the indexing model from the issue text.