for one news by id:
for list of news:
Two ways I can think of are:
I would go for the first option between those two.
But maybe someone have an even better method.
I would suggest you query data with DAO and format the resultant array to your own format and keys
best way to return custom-formatted model from REST API is use
fields() method: https://www.yiiframework.com/doc/api/2.0/yii-base-model#fields()-detail
Just extend main/common model in api/models and configure
Dependency Injection also may be helpful.