Add Event Schedule Conditional

[tomellis91]

The when calling the AWS events api put-rule and using the rate expression, if the minute is > 1 it requires the expression to be in minutes. On the other side 1 minutes will also fail and is required to be set as 1 minute.

The Below error was seen during a stack update:

{
    "eventSource": "events.amazonaws.com",
    "eventName": "PutRule",
    "sourceIPAddress": "cloudformation.amazonaws.com",
    "userAgent": "cloudformation.amazonaws.com",
    "errorCode": "ValidationException",
    "errorMessage": "Parameter ScheduleExpression is not valid.",
    "requestParameters": {
        "name": "<Obfuscated>",
        "scheduleExpression": "rate(3 minute)"
    }
}

The below commands have been run to confirm:

# Validation Error
aws events put-rule --name "AutoscalingFunctionTimer" --schedule-expression "rate(3 minute)"
# Validation Error
aws events put-rule --name "AutoscalingFunctionTimer" --schedule-expression "rate(1 minutes)"

# successful request
aws events put-rule --name "AutoscalingFunctionTimer" --schedule-expression "rate(2 minutes)"
# successful request
aws events put-rule --name "AutoscalingFunctionTimer" --schedule-expression "rate(1 minute)"

[tomellis91]

Hey @triarius,
This should fix some of the issues people have experience when upgrading to v6.

[triarius]

Thanks for raising this @tomellis91. We've decided to go with a slightly different route and make uses specify the unit in the parameter value: #102

We also took the opportunity to rename the parameter to EventSchedulePeriod.

I'll hold off from merging that if you want to incorporate those changes into your PR.

[triarius]

@tomellis91 we decided to merge #102 instead of this.

[tomellis91]

#102

Sounds great, thanks 🙌