validation and check in cron scaler for same start and end case

[Ritikaa96]

Signed-off-by: Ritikaa96 ritika@india.nec.com

Provide a description of what has been changed
In corn scaler, the target doesn't scale down when the start and end schedule are given the same input.

Checklist

• Commits are signed with Developer Certificate of Origin (DCO - learn more)
• Tests have been added
• A PR is opened to update our Helm chart (repo) (if applicable, ie. when deployment manifests are modified)
• A PR is opened to update the documentation on (repo) (if applicable) Cron: adding note for improvement keda-docs#515
• Changelog has been updated

Fixes #2031

[Ritikaa96]

@zroubalik @ahmelsayed PTAL

[ahmelsayed]

I'd add a note to the docs here (https://github.com/kedacore/keda-docs/blob/master/content/docs/2.5/scalers/cron.md) about this error case. @tomkerkhove what do you think?

[tomkerkhove]

Agreed! Let's add it to all versions where CRON is available.

[zroubalik]

@Ritikaa96 looking good, could you please add a note to the Changelog (Improvements section) and add note to the docs as @ahmelsayed mentioned. Thanks!

[Ritikaa96]

@Ritikaa96 looking good, could you please add a note to the Changelog (Improvements section) and add note to the docs as @ahmelsayed mentioned. Thanks!

Sure @zroubalik. Working on it.

[Ritikaa96]

@zroubalik @ahmelsayed @tomkerkhove
Added the note in docs with kedacore/keda-docs#515
updated the changelog as well. PTAL

[ahmelsayed]

Thanks @Ritikaa96