S3Path: support for using access points

[nickrobinson251]

i would like to start accessing an S3 bucket via an "access point"

• https://aws.amazon.com/s3/features/access-points/
• https://docs.aws.amazon.com/AmazonS3/latest/userguide/using-access-points.html
  e.g. instead of s3://bucket/object use arn:aws:s3:us-west-2:123456789012:accesspoint/test/object

My code currently uses S3Paths, so i hoped it'd be as simple as changing S3Path("s3://bucket/object") -> S3Path("s3://arn:aws:s3:us-west-2:123456789012:accesspoint/test/object"), but it seems S3Path isn't able to handle access points being used in place of buckets; currently it mangles the "bucket" name:

julia> S3Path("s3://arn:aws:s3:us-west-2:123456789012:accesspoint/test/object")
p"s3://arn/test/object"

julia> ans.bucket
"arn"

[nickrobinson251]

a workaround is to use a bucket-style alias for the access point
https://docs.aws.amazon.com/AmazonS3/latest/userguide/access-points-alias.html

[nickrobinson251]

If we decide not to support the access point ARN and instead require the use of a bucket-style alias, then i think this issue can be resolved by just adding documentation about using ARNs with S3Path

[omus]

Based upon the documentation I've read so far I think supporting access points would use the S3Path(bucket, key) constructor rather than using the URI based constructor (I've yet to see an example where "s3://$(bucket_arn)/..." is used). In fact this constructor already seems to work with ARNs:

julia> S3Path("s3://arn:aws:s3:us-west-2:123456789012:accesspoint/test", "object")
p"s3://arn:aws:s3:us-west-2:123456789012:accesspoint/test/object"

julia> S3Path("s3://arn:aws:s3:us-west-2:123456789012:accesspoint/test/object")
p"s3://arn/test/object"

I think to better support access points we should error when an ARN is provided via the URI constructor and not display an access point in the URI format as it cannot be parsed that way.

I'm also reminded of #226 here as this is another example of S3 paths being different from a file system path