HTTP method options

[fazpu]

Implement a way to specify which options should given http method have:

post(url: string, body: any | null, options: {
    headers?: HttpHeaders | {
        [header: string]: string | string[];
    };
    observe?: HttpObserve;
    params?: HttpParams | {
        [param: string]: string | string[];
    };
    reportProgress?: boolean;
    responseType?: 'arraybuffer' | 'blob' | 'json' | 'text';
    withCredentials?: boolean;
} = {}): Observable<any>