SDDCs in a group are not in linked mode

[kremerpatrick]

Describe the bug

There is a recent change in the behavior of SDDC Groups. Previously, something like this:

resource "vmc_sddc_group" "sddc_group" {
  name            = var.sddc_group_name
  description     = var.sddc_group_description
  sddc_member_ids = [vmc_sddc.sddc_a.id, vmc_sddc.sddc_b.id]
}

would result in an SDDC group with SDDC A and SDDC B as members, and they would be in linked mode. This is no longer the case, the SDDCs are not linked.

It's not exactly a regression - since you can link and unlink in the UI, it could be argued that the act of creating an SDDC Group should NOT default to having the link enabled. However, that's how it was working until recently, so it's kind of a regression. Now, SDDCs in a group are not linked, and there is no option in this provider for them to be linked.

This might be a feature request instead, but it's not behaving the way it used to so I started with a bug report

Reproduction steps

1. Create an SDDC group with this provider
2. The SDDCs in the group will not be in linked mode.

Expected behavior

Previous behavior is that the SDDCs would be in linked mode. It is probably correct that the SDDCs do not default to linked mode. However, this provider needs a way for linked mode to be specified.

Additional context

No response