Support S3-compliant storages

[normanrz]

Detailed Description

Many self-hosted storage services (e.g. minio) or hosted storage services (e.g. Cloudflare, Backblaze) implement the S3 API. These services are quite popular due to their lower operating costs. It would be great if we would support them as well. For that we should encode the API endpoint in the URI as well:
s3://s3.us-east-1.amazonaws.com/bucket_name/path. For end-users, the explore route could also check the s3://bucket_name/path scheme

[normanrz]

This command should start a local S3-compliant minio server:

MINIO_ROOT_PASSWORD=TtnuieannGt2rGuie2t8Tt7urarg5nauedRndrur MINIO_ROOT_USER=ANTN35UAENTS5UIAEATD minio server --address :8000 ./minio_data