S3 endpoint compatibility

[CEikermann]

Is your feature request related to a problem? Please describe.
Right now you can not use nginx-s3-gateway as a s3 endpoint compatible proxy.
It is not possible to use any S3 library with overwriting the s3 endpoint towards the nginx-s3-gateway.
Background usecase: we want to cache files locally when using the AWS SDK

Describe the solution you'd like
It would be great if the nginx could can be adjust to support this use case. See more details in the additional context

Additional context

• 1.) Run the nginx-s3-gateway on localhost:8000

• 2.) aws --endpoint-url http://localhost:8000 --debug s3 cp s3://any-bucket-name/any-file-path.txt .

• nginx-s3-gateway is not support this case, as its calls the following url: http://localhost:8000/any-bucket-name/any-file-path.txt

• This way also the AWS SDK is emitting S3 request when using s3 endpoint url overwrite

• It would be great, if we can support this case, maybe but adding a location part into the nginx conf which listens on /{S3_BUCKET_NAME} - this should solve the problem already

Looking forward to your reply on this