fix: read one-sided booking times as "ab" and "bis"

tests/Model/TimeRangeTest.php

@@ -149,6 +149,14 @@ class TimeRangeTest extends TestCase
         self::assertSame('yes', $twig->render('t', ['range' => TimeRange::wholeDay()]));
     }
 
+    public function testAOneSidedRangeReadsAsAbOrBis(): void
+    {
+        self::assertSame('bis 13:00', (string) TimeRange::fromMinutes(TimeRange::DAY_START, 13 * 60));
+        self::assertSame('ab 13:00', (string) TimeRange::fromMinutes(13 * 60, TimeRange::DAY_END));
+        self::assertSame('09:00–13:00', (string) TimeRange::fromMinutes(9 * 60, 13 * 60));
+        self::assertSame('ganztägig', (string) TimeRange::wholeDay());
+    }
+
     /**
      * @param list<TimeRange> $ranges
      *