task: add DTO mappers from OpenAPI SDK

[OlegMakarenko]

import {
	ExampleDTO,
	ExampleDTOFromJSON,
} from '@openapi/api-spec';

export class ExampleService {
	public static convertToExampleDTO(exampleObj: IExampleObj): ExampleDTO {
		return ExampleDTOFromJSON(exampleObj);
	}
}