This PR introduces the following behavior for JDBC sources:
Instead of streamName = schema.tableName, this is now streamName = tableName and namespace = schema. This means that, when replicating from these sources, data will be replicated into a form matching the source. e.g. public.users (postgres source) -> public.users (postgres destination) instead of current behaviour of public.public_users. Since MySQL does not have schemas, the MySQL source uses the database as it's namespace.
To do so:
- Make namespace a field class concept in Airbyte Protocol. This allows the source to propagate namespace and destinations to write to a source-defined namespace. Also sets us up for future namespace related configurability.
- Add an optional namespace field to the AirbyteRecordMessage. This field will be set by sources that support namespace.
- Introduce AirbyteStreamNameNamespacePair as a type-safe manner of identifying streams throughout our code base.
- Modify base_normalisation to better support source defined namespace, specifically allowing normalisation of tables with the same name to different schemas.
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