Restore CI test for case-sensitive identifiers when generating sources

[dbeatty10]

resolves #184

Problem

The integration test for the #168 feature was removed in https://github.com/dbt-labs/dbt-codegen/pull/174/files.

Solution

Restore the test that was removed and make updates as-needed so that it works across databases.

This was possible for dbt-redshift because in the interim, we had already updated the enable_case_sensitive_identifier setting to true in the cluster’s parameter group via the Amazon Redshift console. Backstory accessible via dbt-labs/dbt-utils#792 (review).

But the integration for dbt-snowflake still isn't the way we'd like it to be ideally:

Important

It is currently not possible in dbt-snowflake to make a seed with a quoted identifier. So this PR hardcodes an uppercase identifier for Snowflake to align with that behavior. But we should update this if/when dbt-labs/dbt-adapters#178 or dbt-labs/dbt-core#2986 is implemented.

Opened #195 to address this piece separately.

Checklist

• This code is associated with an issue which has been triaged and accepted for development.
• I have verified that these changes work
• I have updated the README.md (if applicable)
• I have added tests & descriptions to my models (and macros if applicable)