[Feature] Add class table to staging tables

### Is there an existing feature request for this?

- [X] I have searched the existing issues

### Describe the Feature

I use this dbt package along with fivetran to create a P&L report of QuickBooks data. However, in my use case, I want to be able to reference the class name, which becomes a hassle if I have to go into each individual schema (I have 18 companies). Can you please add the class table as a staging table so I have access to the unionized data?

### Describe alternatives you've considered

I am in the process of creating my own staging table with the unionized data but thought I would give it a shot to ask the experts.

### Are you interested in contributing this feature?

- [ ] Yes.
- [X] Yes, but I will need assistance and will schedule time during your [office hours](https://calendly.com/fivetran-solutions-team/fivetran-solutions-team-office-hours) for guidance.
- [ ] No.

### Anything else?

_No response_

No files or tests are named in the issue. Start by reviewing the existing QuickBooks staging-table models and the unionized data path; done means class names are available from a shared staging table across the 18 companies.

Written by the indexing model from the issue text.