prepare release 1.15 (#2707)

* bump version
* fix invisible class on labels
* fail safe removal of foreign key
* check if optional form field exists before accessing it
* silently ignore stopped timesheets
* prevent colliding parameter names
* make sure decimal duration is always rendered with two decimals
* simplify translation
* fix #2751 ANSI_QUOTES
* rename composer task
* fix billable statistic rates
* added missing translation for export

src/Migrations/Version20210802174320.php

@@ -27,7 +27,10 @@ final class Version20210802174320 extends AbstractMigration
     public function up(Schema $schema): void
     {
         $teams = $schema->getTable('kimai2_teams');
-        $teams->removeForeignKey('FK_3BEDDC7F8F7DE5D7');
+        // @see https://github.com/kevinpapst/kimai2/issues/2706
+        if ($teams->hasForeignKey('FK_3BEDDC7F8F7DE5D7')) {
+            $teams->removeForeignKey('FK_3BEDDC7F8F7DE5D7');
+        }
         $teams->dropColumn('teamlead_id');
     }