feat(shared): create time functions

shared/tests/datetime_test.py

@@ -0,0 +1,15 @@
+from datetime import time
+
+from pytest import approx
+
+from libretime_shared.datetime import time_in_milliseconds, time_in_seconds
+
+
+def test_time_in_seconds():
+    value = time(hour=0, minute=3, second=34, microsecond=649600)
+    assert time_in_seconds(value) == approx(214.65, abs=0.009)
+
+
+def test_time_in_milliseconds():
+    value = time(hour=0, minute=0, second=0, microsecond=500000)
+    assert time_in_milliseconds(value) == 500