Modify fct_model_directories model to handle staging model dependent on multiple sources

[BradCr]

This is a:

• bug fix PR with no breaking changes
• new functionality

Link to Issue

Closes #111

Description & motivation

Description from the Issue: In fct_model_directories we're specifying staging_models that have an incorrect file path based on their upstream source dependencies. However, if a staging model is dependent on multiple sources (against our best practices, and will cause a warning for other checks in this package, but alas it could still happen) then there will be multiple records for the staging model potentially indicating multiple different values for change_file_path_to. This means that you may be unable to resolve the warnings from this check in the case where your staging model depends on 2 different sources (defined in 2 different directories).

I added a CTE to count number of sources in a staging model, and then listagg() them into a single change_file_path_to column explaining the user should split into two staging models in their appropriate folders..

I haven't added any scenarios to the integration tests yet, which is why I have put this PR into draft mode for now.

I haven't yet updated the documentation for fct_model_directories, but that is something I can do before requesting final review of the PR.

Integration Test Screenshot

Not available yet.

Checklist

• I have verified that these changes work locally on the following warehouses (Note: it's okay if you do not have access to all warehouses, this helps us understand what has been covered)
  • BigQuery
  • Postgres
  • Redshift
  • Snowflake
  • Databricks
  • DuckDB
  • Trino/Starburst
• I have updated the README.md (if applicable)
• I have added tests & descriptions to my models (and macros if applicable)