SchemaResolver class is not testable for resolution of `https://` related refs

Problem:

The SchemaResolver class performs the task of resolving all kinds of references provided in request. The references are provided with $ref keyword. The references could be internal one, pointing to a schema within the system or it could be external reference, like this one '"$ref": "https://geojson.org/schema/FeatureCollection.json"'. These are resolved by making https calls to given URL, like this:

CloseableHttpClient httpClient = HttpClientBuilder.create().build();
            HttpGet getRequest = new HttpGet(url);
            getRequest.addHeader("accept", "application/json");
            HttpResponse response = httpClient.execute(getRequest);

Now, this code works absolutely fine, but it's not testable in unit tests.

Ask:

Move out this logic to a resolve external schemas to a new class, something like ExternalSchemaResolver and use it in has-a relationship with SchemaResolver.

@pbehede assigning this to you. Please reassign accordingly.