scaleway_iam_group_membership support multiple memberships

[Gnoale]

Summary

Change the scaleway_iam_group_membership resource to support list of user ID and / or application ID

Use the SDK endpoint SetGroupMembers to make batch updates (HTTP PUT) instead of single POST / DELETE
=> implement a little exponential retry because the API returns sometimes HTTP 409 with a transient state status in the message

Implement the Update method

Terraform resource breaking change

scaleway_iam_group_membership

• user_id string => user_ids TypeList string
• application_id string => application_ids TypeList string

TF code example

locals {
  users = [
    {
      email    = "[email protected]"
      username = "amember"
    },
    {
      email    = "[email protected]"
      username = "amember2"
    },
    {
      email    = "[email protected]"
      username = "amember3"
    },
    {
      email    = "[email protected]"
      username = "amember4"
    },
  ]
}

resource "scaleway_iam_user" "users" {
  count    = length(local.users)
  email    = local.users[count.index].email
  username = local.users[count.index].username
}

resource "scaleway_iam_group" "misc" {
  name                = "misc"
  external_membership = true
}

resource "scaleway_iam_group_membership" "misc" {
  group_id = scaleway_iam_group.misc.id
  user_ids = [for user in scaleway_iam_user.users : user.id]
}

State sample

# scaleway_iam_group_membership.misc:
resource "scaleway_iam_group_membership" "misc" {
    application_ids = []
    group_id        = "cec91dd4-b87e-4a52-a936-b14301343e66"
    id              = "cec91dd4-b87e-4a52-a936-b14301343e66/user:5b2e896c-a4d3-48e6-83bf-16be9cd0018c,user:7e300e43-7ded-48ff-a18e-8ac7c9b50e0f,user:d33004cd-84d8-46dc-b701-a3ddce46b685,user:bee1e0ea-bd9a-415a-9a04-24d3227b61f1"
    user_ids        = [
        "5b2e896c-a4d3-48e6-83bf-16be9cd0018c",
        "7e300e43-7ded-48ff-a18e-8ac7c9b50e0f",
        "d33004cd-84d8-46dc-b701-a3ddce46b685",
        "bee1e0ea-bd9a-415a-9a04-24d3227b61f1",
    ]
}

fixes #3122