Expose S3 endpoint setting via config file

To use non-AWS services like Google Cloud Storage or a custom provider via S3 compatibility, the endpoint needs to be configurable, and separated from the URL to allow Cloudflare etc proxy for SSL termination.

eg for GCS in S3 mode with custom domain:
AWS_ENDPOINT="https://storage.googleapis.com"
AWS_URL="https://i.pitchfork.club"

This is already supported via the driver, it just needs a config option to feed it in.

https://laracasts.com/discuss/channels/laravel/custom-file-driver-digital-ocean-spaces?page=1

config/filesystems.php

@@ -62,6 +62,7 @@ return [
             'region'   => env('AWS_DEFAULT_REGION'),
             'bucket'   => env('AWS_BUCKET'),
             'url'      => env('AWS_URL'),
+            'endpoint' => env('AWS_ENDPOINT'),
         ],
 
     ],