Fix account deletion (#398)

Why
---
The FxA broker doesn’t wait for a response before re-trying an event.
This means event-handling needs to be idempotent.  Account deletion is
not currently idempotent.  This is leading to needless retries and a
noisy log.

What
----
* Replace `Dash.fxa_uid_to_deleted_list!/1` with the idempotent
  `fxa_uid_to_deleted_list/1`

lib/dash.ex

@@ -273,9 +273,9 @@ defmodule Dash do
     :ok
   end
 
-  @spec fxa_uid_to_deleted_list!(String.t()) :: :ok
-  def fxa_uid_to_deleted_list!(fxa_uid) when is_binary(fxa_uid) do
-    Dash.Repo.insert!(%Dash.DeletedFxaAccount{fxa_uid: fxa_uid})
+  @spec fxa_uid_to_deleted_list(String.t()) :: :ok
+  def fxa_uid_to_deleted_list(fxa_uid) when is_binary(fxa_uid) do
+    Dash.Repo.insert(%Dash.DeletedFxaAccount{fxa_uid: fxa_uid})
     :ok
   end
 

lib/dash_web/fxa_events.ex

@@ -48,12 +48,12 @@ defmodule DashWeb.FxaEvents do
       nil ->
         Logger.warn("FxA account deletion error: No account for fxa_uid to delete")
 
-        Dash.fxa_uid_to_deleted_list!(fxa_uid)
+        Dash.fxa_uid_to_deleted_list(fxa_uid)
         :ok
 
       %Dash.Account{} ->
         Dash.Account.delete_account_and_hubs(account)
-        Dash.fxa_uid_to_deleted_list!(fxa_uid)
+        Dash.fxa_uid_to_deleted_list(fxa_uid)
     end
   end
 

test/dash_test.exs

@@ -95,7 +95,7 @@ defmodule DashTest do
   describe "was_deleted?/1" do
     test "if on deleted list, should return true" do
       fxa_uid = "fxa_uid_test"
-      Dash.fxa_uid_to_deleted_list!(fxa_uid)
+      Dash.fxa_uid_to_deleted_list(fxa_uid)
 
       assert true === Dash.was_deleted?(fxa_uid)
     end
@@ -107,12 +107,12 @@ defmodule DashTest do
     end
   end
 
-  describe "fxa_uid_to_deleted_list!/1" do
+  describe "fxa_uid_to_deleted_list/1" do
     test "adds fxa_uid to the deleted list" do
       fxa_uid = "fxa_uid_test"
       false = Dash.was_deleted?(fxa_uid)
 
-      Dash.fxa_uid_to_deleted_list!(fxa_uid)
+      Dash.fxa_uid_to_deleted_list(fxa_uid)
       assert Dash.was_deleted?(fxa_uid)
     end
   end

test/plugs/auth_test.exs

@@ -179,7 +179,7 @@ defmodule DashWeb.Plugs.AuthTest do
   describe "account was deleted tests" do
     test "returns 401, if account was deleted", %{conn: conn} do
       fxa_uid = get_default_test_uid()
-      Dash.fxa_uid_to_deleted_list!(fxa_uid)
+      Dash.fxa_uid_to_deleted_list(fxa_uid)
 
       conn =
         conn