fix: namespace should not be required in List API

[vancanhuit]

Related issue(s)

Closes #761

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security. vulnerability, I
  confirm that I got green light (please contact
  security@ory.sh) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

I will review the docs and update it accordingly later.

[zepatrik]

Thanks a lot 👍
There is just one small thing I would improve.

[zepatrik]

Suggested change

	WithMaxDepth(func(n int64) *int64 {
	return &n
	}(int64(depth))),
	WithMaxDepth(pointerx.Int64(int64(depth))),