Applicant Age Settings Config and Checker on Submission

[KelseyKryptic]

As an Event HR Team
I need to be able to set and validate against a minimum age for my staff
So that I can keep track of legal obligations based on the ages of my staff

Acceptance Criteria:

1. Event superusers are able to set a "Staff must be 18 by" or a "Staff must be 21 by" date.

2. Age validation logic <18. Minor Staff Not Allowed.
   GIVEN Staff applicant is under 18 for the date specified by the user for the event
   AND Staff applicants < 18 = OK is NOT enabled (default setting)
   WHEN the [Birthdate] field is entered AND the user does not meet age criteria
   THEN User should receive a notification in red text on the form, notifying them "Persons under 18 are ineligible to staff [Event Name]"
   AND they should not be allowed to proceed to the next page or submit their application

3. Enable staff under 18
   GIVEN superusers want to allow staff under 18
   WHEN they enable this functionality
   THEN require the superuser to upload a .pdf, .doc, or .docx file of the under 18 permission form

4 Age validation logic <18. Minor staff allowed with parent/guardian consent
GIVEN an applicant submits their staff application WHEN they are found to be under age 18 by the target date
THEN on their thank you page, they will be notified, "Due to age requirements, we require approval from your parent or guardian in order to consider your staff application. You will receive an email shortly containing the permission form. When we receive the form signed by your guardian, we can move forward with your application."
AND send an automated email to the applicant's email address with the minor volunteer permission form.
AND set status to "Awaiting Parental Consent"

5. Age validation logic >18
   GIVEN an applicant is over the age of 18
   WHEN the applicant submits their application
   AND They are confirmed not to be on the flagged individuals list
   THEN Send an automated email to the applicant thanking them for their application so they know it went through
   AND set status "Pending Director Review"