Implement date validation function

[effone]

Rework of earlier attempt #3212
This will address first task of #4015

Resolve #1071

Tasks:

• Implement date validation function (cleanup)
• Convert forwarding to error page to inline error (eg. return date in past)
• UserCP Away Date : Validate away date
• UserCP Away Date : Move all validations to datahandler
• UserCP Away Date : Enable missing away date error trigger (code in place, never occurs)
• UserCP Birthday : Validate through function
• ModCP Birthday
• ModCP Away Date
• ACP Birthday
• ACP Away Date
• Calendar Start End
• Delay Moderation date validation check

... this will increase as I dig in.

[effone]

@effone what do you mean by syntax correction? You mean spell-checking?

No, it was being failed for auto check PHP Syntax Check / lint (ubuntu-latest, 5.3)
Apparently it came out as a mistake. Thanks @euantorano for implementing the checks making life easier.

[euantorano]

@effone what do you mean by syntax correction? You mean spell-checking?

No, it was being failed for auto check PHP Syntax Check / lint (ubuntu-latest, 5.3)
Apparently it came out as a mistake. Thanks @euantorano for implementing the checks making life easier.

It definitely makes my life easier when reviewing :D

[Eldenroot]

I havent found any other places... would be nice to have this in 1827 :)

[effone]

No there are many places left in MCP & ACP
I need to cover time validation as well along with date. Need to manage some times to modify the function covering time validation.