[MM-53454] Add export file settings + slash command for public link (#23915)

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/notification_push_test.go

@@ -1454,13 +1454,15 @@ func TestPushNotificationRace(t *testing.T) {
 			ConfigStore: memoryStore,
 		},
 		platform.SetFileStore(&fmocks.FileBackend{}),
+		platform.SetExportFileStore(&fmocks.FileBackend{}),
 		platform.StoreOverride(mockStore))
 	require.NoError(t, err)
 	serviceMap := map[product.ServiceKey]any{
-		ServerKey:            s,
-		product.ConfigKey:    s.platform,
-		product.LicenseKey:   &licenseWrapper{s},
-		product.FilestoreKey: s.FileBackend(),
+		ServerKey:                  s,
+		product.ConfigKey:          s.platform,
+		product.LicenseKey:         &licenseWrapper{s},
+		product.FilestoreKey:       s.FileBackend(),
+		product.ExportFilestoreKey: s.ExportFileBackend(),
 	}
 	ch, err := NewChannels(serviceMap)
 	require.NoError(t, err)