Fix S3 public bucket configuration

[fblupi]

🎩 What? Why?

The previous configuration was not working as expected as it returned true every time an environment variable AWS_PUBLIC existed, ignoring its value.

This configuration will only include the line public: true in the s3 storage configuration if the environment variable exists and the value is different than 0, false, or no.

📌 Related Issues

• Related to Allow configuring public S3 #579

[davidbeig]

Perfect!