Closes #10945: Enable recurring execution of scheduled reports & scripts (#11096)

* Add interval to JobResult

* Accept a recurrence interval when executing scripts & reports

* Cleaned up jobs list display

* Schedule next job only if a reference start time can be determined

* Improve validation for scheduled jobs

netbox/extras/migrations/0079_scheduled_jobs.py

@@ -1,3 +1,4 @@
+import django.core.validators
 from django.db import migrations, models
 
 
@@ -13,6 +14,11 @@ class Migration(migrations.Migration):
             name='scheduled',
             field=models.DateTimeField(blank=True, null=True),
         ),
+        migrations.AddField(
+            model_name='jobresult',
+            name='interval',
+            field=models.PositiveIntegerField(blank=True, null=True, validators=[django.core.validators.MinValueValidator(1)]),
+        ),
         migrations.AddField(
             model_name='jobresult',
             name='started',