177 nh link add union strategy parameter

[tkirschke]

Description

New optional parameter "union_strategy" for multi-source non-historized links is added.
"union_strategy" can be set to "all" or "distinct", and influences the UNION statement used to combine multiple sources.

Closes #177

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

[remoteworkflow]

Link to workflow summary: https://github.com/ScalefreeCOM/datavault4dbt-ci-cd/actions/runs/12747754846

---

RESULTS for Synapse:
✅ https://github.com/ScalefreeCOM/datavault4dbt-ci-cd/actions/runs/12749410867

---

RESULTS for Postgres:
✅ dbt-tests
✅ dbt-macro-tests

---

RESULTS for BigQuery:
✅ dbt-tests
✅ dbt-macro-tests

---

RESULTS for Redshift:
✅ dbt-tests
✅ dbt-macro-tests

---

RESULTS for Snowflake:
✅ dbt-tests
✅ dbt-macro-tests

---

RESULTS for Exasol:
❌ dbt-tests (cache inconsistency)
✅ dbt-macro-tests

---

RESULTS for Fabric:
✅ https://github.com/ScalefreeCOM/datavault4dbt-ci-cd/actions/runs/12749410867

---

RESULTS for Oracle:
✅ dbt-tests
✅ dbt-macro-tests

---

RESULTS for Databricks:
✅ dbt-tests
✅ dbt-macro-tests

[tkiehn]

Table in docs was updated with the new parameter