resolves #181
docs dbt-labs/docs.getdbt.com/#

Problem

Currently the unique_key must be a string. It can be a column name or an expression. This PR changes it so it can be a list of column names or expressions.

Solution

This is modeled off of this PR: dbt-labs/dbt-core#4618

It checks if the unique_key is a list and modifies the code based on that. I am open to other approaches if we want something different (maybe turning a string unique_key into an array one element long?).

I couldn't find tests for the existing snapshot macros, so I'm also open to feedback on the best way to add tests for this feature. I have tested this by copying the macros to one of my dbt projects and running it with a modified version of dbt-core that allows a list for the unique_key.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development, and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc.) or this PR has already received feedback and approval from Product or DX