Issue #3353650: Provide cache context for UserCountry condition

src/CacheContext/CountryCodeCacheContext.php

+<?php
+
+namespace Drupal\smart_ip\CacheContext;
+
+use Drupal\Core\Cache\CacheableMetadata;
+use Drupal\Core\Cache\Context\CacheContextInterface;
+use Drupal\smart_ip\SmartIpLocationInterface;
+
+/**
+ * Defines the CountryCodeCacheContext service, for "by country code" caching.
+ *
+ * Cache context ID: 'smart_ip_location'.
+ */
+class CountryCodeCacheContext implements CacheContextInterface
+{
+  /**
+   * Contains user's location.
+   *
+   * @var \Drupal\smart_ip\SmartIpLocationInterface
+   */
+  protected $location;
+
+  /**
+   * Constructs a CountryCodeCacheContext.
+   *
+   * @param \Drupal\smart_ip\SmartIpLocationInterface $location
+   *   Smart IP's data location.
+   */
+  public function __construct(SmartIpLocationInterface $location) {
+    $this->location = $location;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getLabel()
+  {
+    return t('Cache context by country code.');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getContext()
+  {
+    $user_country = $this->location->get('countryCode');
+    return \sha1($user_country);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheableMetadata()
+  {
+    return new CacheableMetadata();
+  }
+
+}