fix: #33 fix source test results saving

[il-dat]

resolves #33

This is a:

• documentation update
• bug fix with no breaking changes
• new functionality
• a breaking change

All pull requests from community contributors should target the main branch (default).

Description & motivation

• Fix: The sources' test results can not be saved due to that the Relation object is returned as 'str' unexpectedly
• New: Adapt dbt v1.8

Checklist

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

[il-dat]

To fix CI later, locally checks all good ✅