[Feature] Show model-level constraints (PK, FK) in dbt docs

[thmswt]

Is this a new bug in dbt-core?

• I believe this is a new bug in dbt-core
• I have searched the existing issues, and I could not find an existing issue for this bug

Current Behavior

When defining constraints on model-level in the schema.yml file and then executing dbt docs generate && dbt docs serve, the columns constraint is not set.

Expected Behavior

The CONSTRAINT value should be set to PK for this example.
More generally, the expected behavior should be that there is no difference between setting the constraints at the column level or at the model level for the presentation of the value within the dbt documentation.

Steps To Reproduce

Initiate and configure a dbt project with:
dbt init

Add the model-level constraint to the my_first_dbt_model model:

constraints:
      - type: primary_key
        columns: [id]

Run dbt docs generate && dbt docs serve

The CONSTRAINT value is empty for the column id:

Relevant log output

No response

Environment

- OS: macOS Sequoia 15.2
- Python: 3.11.11
- dbt: 
Core:
  - installed: 1.9.1
  - latest:    1.9.1 - Up to date!

Plugins:
  - bigquery: 1.9.0 - Up to date!

Which database adapter are you using with dbt?

bigquery

Additional Context

No response

[dbeatty10]

Thanks for reaching out about this @thmswt !

What you are saying makes sense 💡 This is a feature request for the dbt-docs repo, so I've transferred this from https://github.com/dbt-labs/dbt-core/issues/11198 to #536 and updated labels accordingly. This is also covered in #507 (which had been closed as "stale"), so I'm going to re-open the original one and close this one as a duplicate.