Checking for object existence

[Palladinium]

Is your feature request related to a problem? Please describe. There is currently no way to check whether an object exists in a bucket. The README has a link to an exists function, but the method doesn't actually exist: https://github.com/durch/rust-s3/blob/5105a1bff57827f88fb90840f03193665ea34d68/README.md?plain=1#L77

Describe the solution you'd like Adding an exists method to the Bucket API.

Describe alternatives you've considered I've tried using get_object or head_object and checking for the error variant, but I have no idea which S3Error variant is returned when the object doesn't exist vs when anything else goes wrong with fetching the object's data.

[Palladinium]

It looks like the error value returned when an object doesn't exist is S3Error::Http(404, _). It'd still be nice to get this as its own feature. Note that without the ListBucket permission, you will always get a 403 instead, and you tell whether an object doesn't exist or you just can't access it - this is by design in S3's API.

[LockedThread]

I second this

[LockedThread]

It looks like the error value returned when an object doesn't exist is S3Error::Http(404, _). It'd still be nice to get this as its own feature. Note that without the ListBucket permission, you will always get a 403 instead, and you tell whether an object doesn't exist or you just can't access it - this is by design in S3's API.

I cannot even see a way to get the StatusCode because we lose it in the InvalidStatusCode error creation.