forked from loafle/openapi-generator-original
* Cleanup the existing model template
* `{{^isContainer}}foobar{{/isContainer}}{{^isContainer}}` is equivalent to `{{^isContainer}}foobar`
* Add indentations to make it easier to read the template. The generated code is
uglier, but it is ok since users are encouraged to reformat anyway
* Add a default value for non-required lists
Closes https://github.com/OpenAPITools/openapi-generator/issues/20777