Merge branch 'feature/expire-request' into 'develop'

feat(rx): adds expireRequest operator

See merge request !40

libs/utils/rx/src/index.ts

 export { httpRetryBackoff, HttpRetryBackoffConfig } from './lib/http-backoff';
+export { expireRequest } from './lib/expire-request';

libs/utils/rx/src/lib/expire-request.ts

+import { Observable, race, throwError, timer } from 'rxjs';
+import { switchMapTo } from 'rxjs/operators';
+
+export const expireRequest = (timeout: number) => <T>(source: Observable<T>): Observable<T> =>
+  race(
+    source,
+    timer(timeout).pipe(
+      switchMapTo(
+        throwError({ message: 'Error: request timeout expired', status: 504 })
+      )
+    )
+  );