Add Drone CI

- Add drone test environment
- Add drone config
- apt phpunit
- Fix api.php
- Fix item.php
- Fix DBStructure
- Check if caching is possible during tests

tests/src/Core/Lock/MemcachedCacheLockTest.php

@@ -17,13 +17,24 @@ class MemcachedCacheLockTest extends LockTest
 	{
 		$configMock = \Mockery::mock(Configuration::class);
 
+		$host = $_SERVER['MEMCACHED_HOST'] ?? 'localhost';
+
 		$configMock
 			->shouldReceive('get')
 			->with('system', 'memcached_hosts')
-			->andReturn([0 => 'localhost, 11211']);
+			->andReturn([0 => $host . ', 11211']);
 
 		$logger = new NullLogger();
 
-		return new CacheLock(new MemcachedCache('localhost', $configMock, $logger));
+		$lock = null;
+
+		try {
+			$cache = new MemcachedCache($host, $configMock, $logger);
+			$lock = new CacheLock($cache);
+		} catch (\Exception $e) {
+			$this->markTestSkipped('Memcached is not available');
+		}
+
+		return $lock;
 	}
 }