feat(codegen:test): coverage x-expanded-relation + x-codegen.queryParams (#3675)

## What

Adding tests to cover `x-expanded-relation` and  `x-codegen.queryParams` handling

## Why

The logic that processes these OAS extension can be complex to reason with. Therefore, we should have automated tests to prevent unintentional regression.

## How

* Focus on `getModels` method and its sub-routines.
* Add coverage to getOperation codegen parsing.
* Add coverage to model and operation spec property.

.changeset/eight-tips-act.md

@@ -0,0 +1,5 @@
+---
+"@medusajs/openapi-typescript-codegen": patch
+---
+
+feat(codegen:test): coverage x-expanded-relation + x-codegen.queryParams