Replacement for TYPO3\CMS\Extensionmanager\Utility\ConfigurationUtility in Typo3 > 8.7

Question

I am currently working on upgrading an existing Typo3 8.7 instance to Typo3 9.5, following along with the instructions in the official docs.

I have a problem though with a custom extension (written by not-me) that uses TYPO3\CMS\Extensionmanager\Utility\ConfigurationUtility to obtain various configuration values used in the extension.

Usage of the class is as follows:

public function getConfiguration(): array
{
    $configuration = $this->baseConfigurationUtility->getCurrentConfiguration('sbb_oauth');
    return array_column($configuration, 'value', 'name');
}

which is in turn used by this method:

public function getConfigurationOption(string $name)
{
    $configuration = $this->getConfiguration();
    return (isset($configuration[$name]) ? $configuration[$name] : null);
}

The other methods in the class all call getConfigurationOption(string $name) in order to get some specific value from the configuration fetched by ConfigurationUtility.

The problem now is that TYPO3\CMS\Extensionmanager\Utility\ConfigurationUtility is no longer present in Typo3 9.5, and I haven't been able to find any official instructions as to how to properly migrate code that uses it, neither by online search nor by looking through the API.

Since I am not a PHP programmer, and I don't have any experience with Typo3 and its extension system (I just inherited the system and am trying to upgrade it as cleanly as I can), I would appreciate any tips/hints, including "please look [link goes here]", in case I've managed to miss something utterly obvious - thanks in advance!