Changes to List business employers for user

the response's body type changed from no type to object for status 200

added the new optional query request parameter assets_summary

removed Paginated subschema #2 from the response body allOf list for the response status 200

added the non-success response with the status 400

added the non-success response with the status 401

added the non-success response with the status 403

added the non-success response with the status 404

added the non-success response with the status 429

added the optional property bookmark to the response with the 200 status

added the required property items to the response with the 200 status

endpoint added