Support prefix on S3 object names

[acj]

Currently, all objects in S3 are placed in the root of the bucket. This makes tusd adoption difficult for existing applications that use a different convention, such as using S3's support for prefixes to place objects in a pseudo-directory like s3://my_bucket/media/incoming/<upload id>. This PR introduces an ObjectPrefix field on S3Store to enable the use of prefixes.

Addresses one of the requests in #207.

[acj]

@Acconut - when you have time, I'd love to get some feedback on this.

[Acconut]

I'm sorry for the delay, I thought I commented on it literally a few hours ago. But maybe I just missed the submit button.

Anyways, I wanted to ask for your reasoning behind this PR. I was wondering about it since the referenced issue #207 took another approach.

[acj]

No worries. My reasoning is mostly what I mentioned above — established applications that have a large collection of existing objects in a directory (prefix) may want newly uploaded files to be placed in that same directory. In our case, the directory is a long-used convention that realistically can't be changed. tusd doesn't currently provide a solution for this since all files are placed at the root of the bucket, and there's no way to override that behavior. My goal here is to provide a simple, non-breaking parameter that solves that problem.

Regarding the other PR, we experimented with using a post-upload hook to move/rename the uploaded files into our existing directory, but the operation was far too slow and unpredictable for our use case.

[Acconut]

Thank you for the detailed information and the nice PR 👍 I am happy to incorporate this feature into tusd.

[ridhozhr10]

guys, i just trying to make this available too in gcs store. and i discover when using prefix with underscore, i get bug because when creating chunk, idx suffix is splitted with underscore.

i think its best to validate prefix name first in startup