Use named types for API request params

[sosnovsky]

 How about we declear types like below so that we can make code easy to read and simple and avoid code duplication?

type JsonRequestParams = {
 method: 'POST' | 'PUT';
 data: Dict<Serializable>;
};

type TextRequestParams = {
 method: 'POST';
 data: string;
 contentType: string;
};

type GetRequestParams = {
 method: 'GET';
 data?: UrlParams;
};

type DeleteRequestParams = {
 method: 'DELETE';
};

params?: JsonRequestParams | TextRequestParams | GetRequestParams | DeleteRequestParams

Originally posted by @ioanmo226 in #5372 (comment)