Add support for caching

[Mulgish]

Is your feature request related to a problem? Please describe. I would like to be able to easily setup http caching in Unirest.

Describe the solution you'd like Unirest.config().cacheConfig()

Describe alternatives you've considered Manual setup which did not seem to work as there is no way to set cache context on Unirest call.

HttpCacheContext context = HttpCacheContext.create();
HttpGet httpget = new HttpGet("http://www.mydomain.com/content/");
CloseableHttpResponse response = cachingClient.execute(httpget, context);

 final CacheConfig cacheConfig = CacheConfig.custom()
                .setMaxCacheEntries(1000)
                .setMaxObjectSize(8192)
                .build();
        final RequestConfig requestConfig = RequestConfig.custom()
                .setConnectTimeout(30000)
                .setSocketTimeout(30000)
                .build();
        final CloseableHttpClient cachingClient = CachingHttpClients.custom()
                .setCacheConfig(cacheConfig)
                .setDefaultRequestConfig(requestConfig)
                .build();
        Unirest.config()
                .httpClient(ApacheClient.builder(cachingClient));

[ryber]

Now that I (and everyone else) is stuck at home for a while I figure I would get moving on this.

I don't want to just use Apache's cache because one of the goals of this project is to get off of Apache as a dependency. So I'm going to do my own caching layer. I'll try and split it up and do something simple and then add some more options. Here is what I was thinking:

MVP Features:

• Cache will essentially just be a LinkedHashMap
• Keys based on request verb, path, & headers
• Ability to set
  • Max depth of cache (number of entries)
  • TTL of entries
• Ability to clear cache

Advanced Features:

• Ability to provide a custom function for calculating keys
• Ability to set
  • Max individual value size
  • Max total cache size
• Ability to provide a backing cache implementation so of someone wants to use ehcache, memcache, or redis they can with minimal work.

Any other thoughts are appreciated.

[ryber]

Complete in 3.8.00 see http://kong.github.io/unirest-java/#caching