@Override
    public void upgrade() {
        if (configService.get(MigrationCompleted.class) != null) {
            LOG.debug("Migration already completed.");
            return;
        }

        var result = this.usersCollections.bulkWrite(List.of(
                new UpdateManyModel<>(Filters.eq(THEME_MODE_KEY, "teint"), Updates.set(THEME_MODE_KEY, "light")),
                new UpdateManyModel<>(Filters.eq(THEME_MODE_KEY, "noir"), Updates.set(THEME_MODE_KEY, "dark"))
        ));

        if (result.wasAcknowledged()) {
            configService.write(new MigrationCompleted(result.getMatchedCount(), result.getModifiedCount()));
        }
    }
@Test
    void alreadyMigrated() {
        thisMigrationHasRun();

        this.migration.upgrade();

        verify(clusterConfigService, never()).write(any());
    }