Date field: Set minimum days for field

Description - Be able to set the date field based off an SLA.  ie On a specific custom form the date selected can't be less than 5 business days from today

Why is this feature important to you - SLAs require time to complete work and requests are asking for dates that are unrealistic. If we can prevent them from requesting 2 days turn around when the standard SLA is 5days it will help set expectations better. 

How would you like the feature to work - On the field we should be able to set the SLA for date selection

Current Behaviour -  We add a descriptive text outlining the SLA but users select whatever they want when entering the date. Even today's date.