[Feature] Add more unique tests to staging models

[fivetran-reneeli]

Is there an existing feature request for this?

• [X] I have searched the existing issues

Describe the Feature

We've noticed that not all models that have composite keys come with uniqueness tests. This will help with data quality when it comes to package updates in the future.

How would you implement this feature?

See above

Describe alternatives you've considered

No response

Are you interested in contributing this feature?

• [X] Yes.
• [ ] Yes, but I will need assistance.
• [ ] No.

Anything else?

No response