feat: enable usage with S3-compatible services

[sergiustheblack]

This safely allows Koel to use songs hosted on non-AWS s3 storage. However, default behaviour is unchanged.

[phanan]

Thanks! Can you point me to the documentation of this feature and the default value?

[sergiustheblack]

it was a challenge to find default value. so I checked sources and default s3cmd config
https://github.com/aws/aws-sdk-php/blob/ff4872f72fac84ce6e384c4f40d30ec7b0d1eeda/src/S3/S3UriParser.php
however I didn't test it myself with AWS. I use another s3 provider.
docs on setting custom endpoint is here
https://docs.aws.amazon.com/sdk-for-php/v3/developer-guide/guide_configuration.html#endpoint
and
https://docs.aws.amazon.com/general/latest/gr/rande.html

[phanan]

Sounds good, thanks!