Add direct debit mandate failure emails

[mariogalic]

https://trello.com/c/fU7a3xTf/111-send-direct-debit-failure-emails

Salesforce will POST:

       {  
          "payload":{  
             ...
             "email_stage": MF1 | MF2 | ... | MF8
          },
          "object_name":"DD_Mandate_Failure__c"
       }

which we map to

      case ("DD_Mandate_Failure__c", "MF1") => "dd-mandate-failure-1"
      case ("DD_Mandate_Failure__c", "MF2") => "dd-mandate-failure-2"
      case ("DD_Mandate_Failure__c", "MF3") => "dd-mandate-failure-3"
      case ("DD_Mandate_Failure__c", "MF4") => "dd-mandate-failure-4"
      case ("DD_Mandate_Failure__c", "MF5") => "dd-mandate-failure-5"
      case ("DD_Mandate_Failure__c", "MF6") => "dd-mandate-failure-6"

which membership-workflow maps to corresponding Braze Campaign API Identifier:

Related PR: https://github.com/guardian/membership-workflow/pull/170

[coveralls]

Pull Request Test Coverage Report for Build 835

• 5 of 10 (50.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.09%) to 71.143%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
handlers/batch-email-sender/src/main/scala/com/gu/batchemailsender/api/batchemail/model/EmailToSend.scala	4	9	44.44%

Totals
Change from base Build 825:	-0.09%
Covered Lines:	1960
Relevant Lines:	2755

---

💛 - Coveralls

[twrichards]

👍

[frj]

Holiday suspensions : cancellation flow UI