feat(Storage): Adding subpath strategy to the List operation

[sebaland]

Description

This PR introduces the subpathStrategy parameter to StorageListRequest.Options and its corresponding SubpathStrategy enum type.

Using this field will affect the results included in the response:

• subpathStrategy: .include: Objects that are included in nested subpaths will be included in the response. This is the default behaviour
• subpathStrategy: .exclude: Objects that are included in nested subpaths are not included in the response, instead their subpaths are included in the excludedSubpaths list.
• subpathStrategy: .exclude(delimitedBy:): Same as above, but it allows to set a custom character as delimiter for subpaths. The delimiter parameter defaults to "/", which is the same as .exclude.

General Checklist

• Added new tests to cover change, if needed
• Build succeeds with all target using Swift Package Manager
• All unit tests pass
• All integration tests pass
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
  • feat(Swift): Adding SubpathStrategy documentation for Storage.List docs#7831
• PR title conforms to conventional commit style
• New or updated tests include Given When Then inline code documentation and are named accordingly testThing_condition_expectation()
• If breaking change, documentation/changelog update with migration instructions

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[harsh62]

LGTM

[thisisabhash]

what happens when the subpath is --subpath-test ?

[sebaland]

In that case, the excluded subpath will be public/[UUID]--

---

From the S3 perspective, here's how it works. You have these objects:

public/[UUID]-test
public/[UUID]--subpath-test

You filter everything that starts with the prefix public/[UUID]-, and both objects still match:

public/[UUID]-test
public/[UUID]--subpath-test 

But since you set the delimiter to -, any object that contains it after the given prefix is gets rolled up until that character. So public/[UUID]--subpath-test is rolled up to the public/[UUID]-- common prefix, because the - character is the very next character after the prefix.
This value is then reported as an excludedSubpath by Amplify.

[thisisabhash]

minor comment