Fix bigquery copy materialization

[m-sche]

resolves #820

Problem

Since dbt 1.5, bigquery's materialization='copy' does not work due to changed structure of model.refs and the introduction of model versioning. It used to be an array of arrays in 1.4, since 1.5 it is an array of dictionaries.

The ref macro currently accepts one mandatory positional argument (name), one optional positional argument (package), and one optional keyword argument (version).

Model versioning docs: https://docs.getdbt.com/docs/collaborate/govern/model-versions
Ref macro arguments docs: https://docs.getdbt.com/reference/dbt-jinja-functions/ref#advanced-ref-usage

Solution

This PR adapts to the new structure of model.refs and allows for an optional version argument.

A functional test has been added to test if a very simple copy/incremental materialization works. This test should catch similar issues in the future. The test fails if executed against the current code and passes when executed against the fixed code in this PR. The test is heavily inspired by test_simple_copy.sql test from this repository.

A similar solution was discussed in #820 but the discussion got stale, hence this PR, but I am keen on receiving any feedback!

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

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[m-sche]

Added a changie entry and fixed an account from which the commits were created

[m-sche]

From my point of view, this PR is ready for review, please let me know if there's anything missing :)

[dbeatty10]

@mikealfare and @dataders:

I just added backport labels for 1.5 and 1.6 per #820 (comment).

What else do we need to do to create backport PRs for these?