Fix removing sticky fields from Pseudonym

When no changes happened for a user and
clear_sis_stickiness flag was on, the
'stuck_sis_field' didn't get cleared on Pseudonym.

This is because the before_save callback didn't
fire in lib/sticky_sis_fields.rb.

By changing the sis_batch_id on the Pseudonym, we
can force an update (and with that clearing the
sticky fields).

Test plan:
 - Import a user
 - Change its login_id to something
 - Do another SIS import, using the same login_id
   and with setting 'Clear UI-changed state'
 - Observe the 'stuck_sis_fields' gets cleared on
   the Pseudonym. Next SIS import will be able to
   overwrite any property

References SOS-2633

flag=none

Change-Id: I80ee45198863785b4c693375bc54557cc13f66e4
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/283658
Reviewed-by: Kozma Jozsef <[email protected]>
Reviewed-by: Richard Zana <[email protected]>
Reviewed-by: August Thornton <[email protected]>
QA-Review: Balazs Komaromi <[email protected]>
Product-Review: Balazs Komaromi <[email protected]>
Tested-by: Service Cloud Jenkins <[email protected]>

lib/sis/user_importer.rb

@@ -405,7 +405,7 @@ def process_batch(login_only: false)
             next
           end
 
-          if pseudo.changed?
+          if pseudo.changed? || (Pseudonym.sis_stickiness_options[:clear_sis_stickiness] && pseudo.read_attribute("stuck_sis_fields").present?)
             pseudo.sis_batch_id = user_row.sis_batch_id if user_row.sis_batch_id
             pseudo.sis_batch_id = @batch.id if @batch
             if pseudo.valid?

spec/lib/sis/user_importer_spec.rb

@@ -74,6 +74,29 @@
     expect(Pseudonym.last.deleted_at).not_to be_nil
   end
 
+  it "clears sticky fields, even when there are no changes for the pseudonym" do
+    account_model
+    Setting.set("sis_transaction_seconds", "1")
+    active_user = SIS::Models::User.new(user_id: "sis_id", login_id: "123", status: "active",
+                                        full_name: "User One", email: "[email protected]")
+    SIS::UserImporter.new(@account, { batch: @account.sis_batches.create! }).process([]) do |importer|
+      importer.add_user(active_user)
+    end
+
+    Pseudonym.where(unique_id: "123").first.tap do |pseudonym|
+      pseudonym.unique_id = "321"
+      pseudonym.save!
+    end
+
+    unchanged_user = SIS::Models::User.new(user_id: "sis_id", login_id: "321", status: "active",
+                                           full_name: "User One", email: "[email protected]")
+    SIS::UserImporter.new(@account, { batch: @account.sis_batches.create!, clear_sis_stickiness: true }).process([]) do |importer|
+      importer.add_user(unchanged_user)
+    end
+
+    expect(Pseudonym.last.read_attribute("stuck_sis_fields")).to eq ""
+  end
+
   it "does not update deleted_at property when user gets deleted but workflow_state is stuck" do
     account_model
     Setting.set("sis_transaction_seconds", "1")