vault list /identity/group/{id,name} returns 404 if no groups exist

[yajo]

Describe the bug
If no groups exist, instead of returning an empty list, the API returns a 404 error.

To Reproduce
Steps to reproduce the behavior:

1. Run vault list /identity/group/id or vault list /identity/group/name when no groups exist.

Expected behavior
It should return 200 with an empty list.

Environment:

• Vault Server Version (retrieve with vault status): 0.11.5
• Vault CLI Version (retrieve with vault version): Vault v0.11.5 ('a59ffa4a0f09bbf198241fe6793a96722789b639')
• Server Operating System/Architecture: Docker image.

Vault server configuration file(s):

  backend:
    file:
      path: /vault/file
  ui: true

Additional context:
The docs say 404 is not an expected return:

• https://www.vaultproject.io/api/secret/identity/group.html#list-groups-by-id
• https://www.vaultproject.io/api/secret/identity/group.html#list-groups-by-name

[ncabatoff]

This appears to be a documentation bug, based on #1365.

[jefferai]

We're thinking over lists and whether they generally be 404 or 204. I'm closing this since we're thinking about it for more than just this specific instance.