feature: add optimize() call to snapshot materialization (#1335) (#1341)

partially resolves #1335

### Description

1. added `optimize()` call to the snapshot materialization, matching
existing behavior in table and incremental materializations. when a
snapshot is configured with `liquid_clustered_by`, `zorder`, or
`auto_liquid_cluster`, the `OPTIMIZE` query will now execute
automatically after each snapshot run.

2. the change is a single-line addition to `snapshot.sql`, placed after
`persist_constraints` and before `post-hooks` (again, consistent with
the pattern in `table.sql` and `incremental.sql`).


**note**: the original issue also mentioned default clustering columns
and `ALTER TABLE` support for config changes. these are intentionally
excluded from this PR to keep scope minimal and can be addressed in
follow-up PRs if needed. i believe they need a design decision that
should be discussed by/with maintainers first due to having a larger
scope.

### Checklist

- [x] I have run this code in development and it appears to resolve the
stated issue (**unit tests pass :** this change mirrors the identical
optimize() call pattern already used in `table.sql` and
`incremental.sql`.)
- [x] This PR includes tests, or tests are not required/relevant for
this PR
- [x] I have updated the `CHANGELOG.md` and added information about my
change to the "dbt-databricks next" section.

---------

Signed-off-by: aarushisingh04 <aarushi07.singh@gmail.com>

Author: aarushisingh04

CHANGELOG.md

@@ -6,6 +6,7 @@
   gated behind the `use_concurrent_microbatch` behavior flag (default: `false`).
   Opt in via `flags: {use_concurrent_microbatch: true}` in `dbt_project.yml`
   ([#914](https://github.com/databricks/dbt-databricks/issues/914))
+- Run `optimize` on snapshots when `liquid_clustered_by`, `zorder`, or `auto_liquid_cluster` config is set, matching existing behavior for tables and incremental models ([#1335](https://github.com/databricks/dbt-databricks/issues/1335))
 
 ### Fixes
 

dbt/include/databricks/macros/materializations/snapshot.sql

@@ -124,6 +124,8 @@
 
   {% do persist_constraints(target_relation, model) %}
 
+  {% do optimize(target_relation) %}
+
   {{ run_hooks(post_hooks, inside_transaction=False) }}
 
   {{ return({'relations': [target_relation]}) }}

tests/functional/adapter/simple_snapshot/test_snapshot.py

@@ -32,6 +32,13 @@ class TestSnapshotCheck(BaseSnapshotCheck):
     pass
 
 
+@pytest.mark.skip_profile("databricks_uc_cluster", "databricks_cluster")
+class TestSnapshotLiquidClustering(TestSnapshot):
+    @pytest.fixture(scope="class")
+    def project_config_update(self):
+        return {"snapshots": {"+liquid_clustered_by": "id"}}
+
+
 @pytest.mark.skip_profile("databricks_cluster")
 class TestSnapshotIceberg(BaseSnapshotCheck):
     @pytest.fixture(scope="class")