Implement ConnectionBuilder in cluster-aware datasource

We want to provide users with API to obtain connection pointing to a specific shard. In general java.sql package this is done via ConnectionBuilder interface as shown in the article.

So cluster-aware API may look similarly

     PicodataClusterAwareDatasource ds = new PicodataClusterAwareDatasource();
     PicodataSharding shardingKey = ds.createShardingKeyBuilder(...)
                           .subkey("PITTSBURGH_BRANCH", JDBCType.VARCHAR)
                           .build();
     Connection con = ds.createConnectionBuilder()
                       .user("rafa")
                       .password("tennis")
                       .setShardingKey(shardingKey)
                       .build(); // take connection from pool and return handle