bugfixes (#3078)

* fix phpdoc
* fix invoice export field order
* prevent empty migration warning
* do not trigger export validation on new timesheets
* update license year
* remove trailing comma in function call for php compatibility
* add new composer plugin config
* bump phpunit schema version

phpunit.xml.dist

@@ -1,12 +1,9 @@
 <?xml version="1.0" encoding="UTF-8"?>
-
-<!-- https://phpunit.de/manual/current/en/appendixes.configuration.html -->
 <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/6.1/phpunit.xsd"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/8.5/phpunit.xsd"
          backupGlobals="false"
          colors="true"
-         bootstrap="tests/bootstrap.php"
->
+         bootstrap="tests/bootstrap.php">
     <php>
         <ini name="error_reporting" value="-1" />
         <ini name="max_execution_time" value="-1" />
@@ -64,9 +61,8 @@
     </filter>
 
     <!--
-        begins a database transaction before every testcase and rolls it back after the test finished, so
-        tests can manipulate the database without affecting other tests
-        @see https://github.com/dmaicher/doctrine-test-bundle
+        wrap tests inside database transactions, so tests can safely manipulate contents without
+        affecting other tests. @see https://github.com/dmaicher/doctrine-test-bundle
     -->
     <extensions>
         <extension class="DAMA\DoctrineTestBundle\PHPUnit\PHPUnitExtension" />