test: Increase test coverage on auditable resources (#7038)

* test: Increase test coverage on auditable resources

When adding a new audit resource, we also need to add it to the
function switch statements. This is a likely mistake, now a unit
test will check this for you

coderd/database/dump.sql

@@ -94,7 +94,8 @@ CREATE TYPE resource_type AS ENUM (
     'api_key',
     'group',
     'workspace_build',
-    'license'
+    'license',
+    'workspace_proxy'
 );
 
 CREATE TYPE user_status AS ENUM (