Updated croner to 8.1.0 and fixed "recurring-interval" type maintenance

[buzzinJohnnyBoi]

⚠️⚠️⚠️ Since we do not accept all types of pull requests and do not want to waste your time. Please be sure that you have read pull request rules:
https://github.com/louislam/uptime-kuma/blob/master/CONTRIBUTING.md#can-i-create-a-pull-request-for-uptime-kuma

Tick the checkbox if you understand [x]:

• I have read and understand the pull request rules.

Description

Fixes #4634
Possibly #4930

Type of change

Please delete any options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Checklist

• My code follows the style guidelines of this project
• I ran ESLint and other linters for modified files
• I have performed a self-review of my own code and tested it
• I have commented my code, particularly in hard-to-understand areas (including JSDoc for methods)
• My changes generates no new warnings
• My code needed automated testing. I have added them (this is optional task)

Screenshots (if any)

Please do not use any external image service. Instead, just paste in or drag and drop the image here, and it will be uploaded automatically.

[CommanderStorm]

overall looks good to me.
Thanks for the work ❤️
I have left a question below

[CommanderStorm]

I need a bit of help understanding the if-clause you added 😅:
Is this not already covered by the if or else branch above?

[buzzinJohnnyBoi]

Hi, @CommanderStorm, so above is an if - else if - else, and the else if is when this.end_date is set, and it calculates if this.end_date will be before the end of the interval. If it is not, then this.duration is left undefined.
I guess my solution is not the best one, I was not sure if it was left undefined for some other purpose, but if it is not, then I guess the else if should look something like this:

else if (this.end_date) {
    let d = dayjs(this.end_date).diff(dayjs(), "second");
    if (d < this.duration) {
        duration = d * 1000;
    }
    else {
        duration = this.duration * 1000;
    }
}

Let me know if you want me to make this change.

[CommanderStorm]

I think that is better.
duration is never explicitly checked for undefined => I think it being undefined is a bug ^^

While you are at it, I think that while if/... clause would be way better if extracted into a function this.duration = this.inferDuration()
That way the controll flow is not as confusing in the future..

[buzzinJohnnyBoi]

    inferDuration(customDuration) {
        // Check if duration is still in the window. If not, use the duration from the current time to the end of the window
        if (customDuration > 0) {
            return customDuration;
        } else if (this.end_date) {
            let d = dayjs(this.end_date).diff(dayjs(), "second");
            if (d < this.duration) {
                return d * 1000;
            }
        }
        return this.duration * 1000;
    }

Code here
Lmk if this is good.

[CommanderStorm]

Thanks for the fix! 🎉

Note

This PR is part of the v2.0 merge window => see #4500 for the bugs that need to be addressed before we can ship this release ^^

_{All changes in this PR are small and uncontroversial ⇒ merging with junior maintainer approval}