We currently don't check whether an existing table actually matches the schema specified in a table creation request, and just assume that it does. We should
- check whether the schema matches (based on the json schema stored in the meta table, but possibly also based on the actual table schema as exposed by system.schema_colums.
- if it does, return success.
- if it does not:
- see if we can do something about it
- else, throw an error.