DBT code version docs (#11692)

### Summary & Motivation

Add some docs for DBT asset code versions.

docs/content/integrations/dbt.mdx

@@ -18,6 +18,7 @@ Dagster orchestrates dbt alongside other technologies, so you can combine dbt wi
 Dagster has built-in support for loading dbt models, seeds, and snapshots as software-defined assets, enabling you to:
 
 - Visualize and orchestrate a graph of dbt assets, and execute them with a single dbt invocation
+- Version your dbt models by their defining SQL code, allowing downstream assets to be automatically marked stale when a model changes
 - View detailed historical metadata and logs for each asset
 - Define Python computations that depend directly on tables updated using dbt
 - Track data lineage through dbt and your other tools

docs/content/integrations/dbt/reference.mdx

@@ -61,7 +61,7 @@ dbt_assets = load_assets_from_dbt_manifest(
 )
 ```
 
-**Note:** if you make any changes to your dbt project that change the structure of the project (such as changing the dependencies of a model or adding a new one), you'll need to regenerate your manifest file for those changes to be reflected in Dagster.
+If you make any changes to your dbt project that change the structure of the project (such as changing the dependencies of a model or adding a new one), you'll need to regenerate your manifest file for those changes to be reflected in Dagster.
 
 ---
 
@@ -191,6 +191,12 @@ dbt_assets = load_assets_from_dbt_project(
 
 ---
 
+## dbt models, code versions, and staleness
+
+Note that Dagster allows the optional specification of a [`code_version`](/guides/dagster/scheduling-assets#step-5-change-code-versions) for each software-defined asset, which is used to track asset staleness. The `code_version` for an asset arising from a dbt model is defined automatically as the hash of the SQL defining the DBT model. This means that changing the code of the model will automatically cause the corresponding asset, and all downstream assets, to be marked stale.
+
+---
+
 ## Defining dependencies
 
 - [Upstream dependencies](#upstream-dependencies)