fix(cron): accept day-of-week 7 as a valid Sunday alias

Standard cron syntax allows weekday values 0–7, where both 0 and 7
mean Sunday (documented in crontab(5) and implemented by vixie-cron,
cronie, fcron, and most Unix cron daemons). The validator was
enforcing a max of 6, rejecting valid expressions like
`* * * * 7`, `0 0 * * 0-7`, and `0 0 * * 0,7`.

Change the weekday upper bound from 6 to 7 and add three test cases
that were previously (incorrectly) rejected.

Author: gaoflow

src/validators/cron.py

@@ -72,7 +72,7 @@ def cron(value: str, /):
         return False
     if not _validate_cron_component(months, 1, 12):
         return False
-    if not _validate_cron_component(weekdays, 0, 6):
+    if not _validate_cron_component(weekdays, 0, 7):
         return False
 
     return True

tests/test_cron.py

@@ -22,6 +22,9 @@
         "0 3-6 * * *",
         "*/15 0,6,12,18 * * *",
         "0 12 * * 0",
+        "0 12 * * 7",
+        "0 0 * * 0-7",
+        "0 0 * * 0,7",
         "*/61 * * * *",
         # "5-10/2 * * * *", # this is valid, but not supported yet
     ],