Plugin to update all the related contacts of specific account when specific field on account record has been updated

: Following are the details of what needs to be covered:

1. Make sure we have Account to Contact (1:N) relationship setup calling the subgrid as Related Contacts
2. Create a new field in Account and Contact both called as “Payment Type” which is an optionset field having options as {Cash, Debit Card, Credit Card}
3. Create a plugin on Account entity which will be registered on “Update” of “Payment Type” field.
4. Plugin logic will include following steps:
   1. Retrieve all related Contacts corresponding to Account in context
   2. Update “Payment Type” field on all the Contacts same as what has been set on updated Account record