If a Dojo Champion is under 18, they need to fill in extra fields on the SAD form

[glenpike]

See https://raspberrypi.monday.com/boards/1236004929/pulses/1396590031

Previously, we required the date-of-birth for a user in the Champion part of the Start A Dojo form:
https://github.com/CoderDojo/cp-zen-platform/blob/master/web/public/js/directives/cd-start-dojo/champion/template.dust#L25-L30

This was filled in with the date of birth for the current user (from the dob column sys_user table)

With Raspberry Pi Accounts, we don't store the DOB anymore, so this field was hidden and it defaults to Unix epoch 0 (1970...) which causes issues for people verifying dojo's.

Under 18's are required to supply a parental name / email which currently remains hidden in the form -
https://github.com/CoderDojo/cp-zen-platform/blob/master/web/public/js/directives/cd-start-dojo/champion/template.dust#L32-L46 - because a DOB of 1970 means they show as over 18, even if they are not.

Proposal:

• We will replace the hidden DOB field with a 'How old are you?' select dropdown similar to the Pi Accounts image below. This will have the ages 13-17, then an '18 or over' option.
• The show / hide of the field should be changed - e.g. getAge to use the value from the select box - if the user is not '18 or over', we will show the other fields.
• We will add 'When is your birthday' fields to the show/hide section. This will be like the fields in the Pi Accounts picture below. With the 'How old are you?' value, we will create a DOB correctly formatted for under 18 users (allowing us to determine when they reach 18)
• Ensure that the DOB and parent details are stored in the 'application' JSON field of the cd_dojoleads table|
• Check if we need to store the dob in the sys_user table (it may still happen anyway)

Picture of Pi Accounts u13 'DOB' form: