Changes to Opens several budgets

added the new project_already_exported enum value to the errors/items/code response property for the response status 409

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 406

added the non-success response with the status 408

added the non-success response with the status 415

added the non-success response with the status 423

added the non-success response with the status 429

added the non-success response with the status 500

endpoint added