feat: provide endpoint to lock/unlock workspace (#8239)

coderd/database/migrations/000131_workspace_locked.down.sql

@@ -0,0 +1,3 @@
+BEGIN;
+ALTER TABLE workspaces DROP COLUMN locked_at;
+COMMIT;

coderd/database/migrations/000131_workspace_locked.up.sql

@@ -0,0 +1,3 @@
+BEGIN;
+ALTER TABLE workspaces ADD COLUMN locked_at timestamptz NULL;
+COMMIT;