Let migrate-dbsql-dashboards command to run as collection (#2656)

## Changes
Let `migrate-dbsql-dashboards` command to run as collection

### Linked issues

Resolves #2612

### Functionality

- [x] modified existing command: `databricks labs ucx
migrate-dbsql-dashboards`

### Tests

- [x] manually tested
- [x] added unit tests
- [ ] ~added integration tests~ : Covering after #2507

labs.yml

@@ -265,6 +265,8 @@ commands:
     flags:
       - name: dashboard-id
         description: (Optional) DBSQL dashboard ID to migrate. If no dashboard ID is provided, all DBSQL dashboards in the workspace will be migrated.
+      - name: run-as-collection
+        description: (Optional) Run the command for the collection of workspaces with ucx installed. Default is False.
 
   - name: revert-dbsql-dashboards
     description: Revert DBSQL dashboards that have been migrated to their original state before the migration.

src/databricks/labs/ucx/cli.py

@@ -563,10 +563,20 @@ def migrate_acls(w: WorkspaceClient, *, ctx: WorkspaceContext | None = None, **n
 
 
 @ucx.command
-def migrate_dbsql_dashboards(w: WorkspaceClient, dashboard_id: str | None = None):
+def migrate_dbsql_dashboards(
+    w: WorkspaceClient,
+    dashboard_id: str | None = None,
+    ctx: WorkspaceContext | None = None,
+    run_as_collection: bool = False,
+    a: AccountClient | None = None,
+) -> None:
     """Migrate table references in DBSQL Dashboard queries"""
-    ctx = WorkspaceContext(w)
-    ctx.redash.migrate_dashboards(dashboard_id)
+    if ctx:
+        workspace_contexts = [ctx]
+    else:
+        workspace_contexts = _get_workspace_contexts(w, a, run_as_collection)
+    for workspace_context in workspace_contexts:
+        workspace_context.redash.migrate_dashboards(dashboard_id)
 
 
 @ucx.command

tests/unit/test_cli.py

@@ -799,9 +799,21 @@ def test_create_missing_principal_azure(ws, caplog):
     assert str(failure.value) == "Unsupported cloud provider"
 
 
-def test_migrate_dbsql_dashboards(ws, caplog):
-    migrate_dbsql_dashboards(ws)
-    ws.dashboards.list.assert_called_once()
+@pytest.mark.parametrize("run_as_collection", [False, True])
+def test_migrate_dbsql_dashboards_list_dashboards(
+    run_as_collection,
+    workspace_clients,
+    acc_client,
+) -> None:
+    if not run_as_collection:
+        workspace_clients = [workspace_clients[0]]
+    migrate_dbsql_dashboards(
+        workspace_clients[0],
+        run_as_collection=run_as_collection,
+        a=acc_client,
+    )
+    for workspace_client in workspace_clients:
+        workspace_client.dashboards.list.assert_called_once()
 
 
 def test_revert_dbsql_dashboards(ws, caplog):