Self-service update billing details for recurring contributions and auto-renew memberships

• If the associated processor supports changes to billing details via api, then recurring contribution and auto-renew membership initial notification, as well as subsequent receipts should include a separate link to "Change Billing Details". Link includes checksum and loads an edit form with fields to enter new Credit Card Information, as well as to update Billing Name and Address fields (these are pre-filled).

• Add same link (but w/o checksum) to Contact Dashboard - recurring contribution and membership selectors if supported by associated processor. 

• If processor request succeeds, insert an Activity record:
  • Add new activity type - "Update Recurring Contribution Billing Details"
  • Activity source contact_id is the contact making the updated (which should be the donor).. Target is also the donor.
  • Activity description should include original "processor_id" and any "update" tracking transaction id's received from processor

NOTE: We don't store the billing name and address in the contribution_recur table - so I'm not sure what to do about storing updates to this value. Simplest solution would be to just dump old and new addresses in the activity description. Open to other ideas. ???

• Update confirmation email should be sent to donor. We can use same message template as for back-office billing detail changes.