Document how to authenticate against s3

[akhenakh]

CSV or Parquet in Duckdb are relying on the c++ httpfs extension,

You can do

CREATE OR REPLACE SECRET secret (
            TYPE s3,
            KEY_ID 'xxx',
            SECRET 'xxxx+xxxx',
            REGION 'us-east-2'
         );

and it will just work.

The Vortex extension, however, is built in Rust and uses the Rust object_store crate which does not set DuckDB's internal SQL-defined secrets.

It does not seem to be documented.

The solution is to set env variables:

export AWS_ACCESS_KEY_ID="your_access_key"
export AWS_SECRET_ACCESS_KEY="your_secret_key"
export AWS_REGION="your_bucket_region"