Handle M2 customer deleted, SP customer not deleted, new M2 customer created

[chrismshea]

PRs: #246

Steps to reproduce:

• A customer can request their account to be deleted on Magento.
• They can then create a new account using the same email address.
• When they create a new subscription they will have created it for a customer in SP that has their old ID.
• We then do the reorder, and attempt to create a cart using the old customer id.

Expected:

• When they create a new subscription, new SP customer record is created
• Old SP customer record gets marked as orphaned, email is changed to: Cur. Email + "-ORPHANED-" + unique ID
• New SP customer record gets their new email and new M2 customer ID

Algorithm

• Lookup SP Customer based on M2 customer ID
  • If found, use it
  • If not found
  • Lookup SP customer based on customer email
    • If not found, create new customer
    • If found
    • Update existing SP customer record, change email to: Cur. Email + "-ORPHANED-" + unique ID
    • Create new customer

[garthbrantley]

@chrismshea Please document steps to reproduce

[chrismshea]

1. On Magento 2 Frontend add a subscription item to your cart and checkout creating a new customer.
2. Note the customer created in Subscribe Pro and in Magento 2 Admin

4. In Magento 2 Admin edit then delete the customer
5. Repeat Step 1 creating a new customer using the same email address as the first time
6. Note the customer id in Magento 2 admin will have incremented 1 past the original
7. Note the customer record in SP still has the original id.

[eugene-shab]

@garthbrantley Added fix for updating platform_specific_customer_id in SP on customer save event

[garthbrantley]

Issue was discussed by @chrismshea @eugene-shab and @garthbrantley - Decided not to implement this at this time.