MM-9728: Online migration for advanced permissions phase 2 (#8744)

* MM-9728: Online migration for advanced permissions phase 2

* Add unit tests for new store functions.

* Move migration specific code to own file.

* Add migration state function test.

* Style fixes.

* Add i18n strings.

* Fix mocks.

* Add TestMain to migrations package tests.

* Fix typo.

* Fix review comments.

* Fix up the "Check if migration is done" check to actually work.

api4/channel_test.go

@@ -12,6 +12,8 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+
 	"github.com/mattermost/mattermost-server/model"
 	"github.com/mattermost/mattermost-server/utils"
 )
@@ -1890,6 +1892,17 @@ func TestUpdateChannelScheme(t *testing.T) {
 
 	th.App.SetLicense(model.NewTestLicense(""))
 
+	// Mark the migration as done.
+	<-th.App.Srv.Store.System().PermanentDeleteByName(model.MIGRATION_KEY_ADVANCED_PERMISSIONS_PHASE_2)
+	res := <-th.App.Srv.Store.System().Save(&model.System{Name: model.MIGRATION_KEY_ADVANCED_PERMISSIONS_PHASE_2, Value: "true"})
+	assert.Nil(t, res.Err)
+
+	// Un-mark the migration at the end of the test.
+	defer func() {
+		res := <-th.App.Srv.Store.System().PermanentDeleteByName(model.MIGRATION_KEY_ADVANCED_PERMISSIONS_PHASE_2)
+		assert.Nil(t, res.Err)
+	}()
+
 	team := &model.Team{
 		DisplayName:     "Name",
 		Description:     "Some description",