allow inheriting from TimeSeries class

[glaszig]

i needed to subclass TimeSeries to add functionality but then was bitten by privateness of things as those properties are exclusive to the defining scope.

this opens up the class to make it easier to quickly modify behavior.

[palicao]

Hi @glaszig, and thank you for your PRs! May I ask you which use case is solved by extending the class, which is not possible to solve using composition?
Whenever possible, we should prefer composition to inheritance!

[glaszig]

to quickly implement the patch in #33. i ended up copying the entire class. but nevermind, i moved to use a delegator/decorator. implementation for reference:

<?php

namespace App;

use Redis;
use Palicao\PhpRedisTimeSeries\AggregationRule;
use Palicao\PhpRedisTimeSeries\Label;
use Palicao\PhpRedisTimeSeries\Metadata;
use Palicao\PhpRedisTimeSeries\Sample;
use Palicao\PhpRedisTimeSeries\TimeSeries;
use Palicao\PhpRedisTimeSeries\Client\RedisClient;
use Palicao\PhpRedisTimeSeries\Client\RedisConnectionParams;
use RedisException;

class RedisTimeSeries
{
    protected $redis, $ts;

    public function __construct()
    {
        $this->redis = new RedisClient(
            new Redis(),
            new RedisConnectionParams()
        );
        $this->ts = new TimeSeries($this->redis);
    }

    public function __call(string $name, array $args)
    {
        return call_user_func_array([$this->ts, $name], $args);
    }

    public function info(string $key): Metadata
    {
        $result = $this->redis->executeCommand(['TS.INFO', $key]);
        $result = $this->parseInfo($result);

        $labels = [];
        foreach ($result['labels'] as $label) {
            $labels[] = new Label($label[0], $label[1]);
        }

        $sourceKey = $result['sourceKey'] === false ? null : $result['sourceKey'];

        $rules = [];
        foreach ($result['rules'] as $rule) {
            $rules[$rule[0]] = new AggregationRule($rule[2], $rule[1]);
        }

        return Metadata::fromRedis(
            $result['lastTimestamp'],
            $result['retentionTime'],
            $result['chunkCount'],
            $result['chunkSize'],
            $labels,
            $sourceKey,
            $rules
        );
    }

    protected function parseInfo($info)
    {
        $chunks = array_chunk($info, 2);
        $props = [];
        foreach ($chunks as $chunk) {
            $props[$chunk[0]] = $chunk[1];
        }

        // maxSamplesPerChunk has been replaced with chunkSize in 1.4.4
        // https://github.com/RedisTimeSeries/RedisTimeSeries/commit/5896a509e5ec30929c04cd96a7f8b2c9e9651ed9
        $props['chunkSize'] = isset($props['chunkSize'])
            ? $props['chunkSize']
            : $props['maxSamplesPerChunk']
            ;

        return $props;
    }
}