Pass list to helm using terraform helm_release provider

Ive seen this and another question similar, but cannot get it to work https://stackoverflow.com/questions/71754003/using-terraforms-helm-release-how-do-i-set-array-or-list-values

My list is coming from a json file which is a list of allowed groups

locals {
  app_groups = jsondecode(file("../../work/resources/gke/params/access_auths.json")).accessgroups[var.project][0].app_group
}
output "app_groups" {
    value = local.app_groups
}

Gives -

app_groups = [
  "bigquery-team",
  "devops-team",
]

main.tf -

resource "helm_release" "oauth2proxy" {
  name         = "oauth2proxy"
  chart        = "../charts/oauth2proxy"
  namespace    = kubernetes_namespace.oauth2proxy.metadata.0.name
  set {
    name  = "app_groups[0]"
    value = "${local.app_groups}"
  }
  values = [
    templatefile("../charts/oauth2proxy/oauth2proxy_values.yaml", {
      projectID     = var.project
      clusterName   = var.clusterName
    })
  ]
}

In helm deployment.yml it needs to go into the -args when starting the container -

      {{  range $v := .app_groups }}
        - --allowed-group="{{ $v }}"
      {{ end }}

But i get

Error: Incorrect attribute value type
 on main.tf line 129, in resource "helm_release" "oauth2proxy":
 129:     value = "${local.app_groups}"
 ────────────────
 │ local.app_groups is tuple with 2 elements
 │ Inappropriate value for attribute "value": string required.

The thing is, it is a tuple, and want it to be a tuple, and i cant see how to tell terraform or helm that its supposed to be a tuple.

Ive tried various different "set" and "dynamic set" but not got anywhere with it.

value expects a string. In Helm you can provide an array using {a, b, c} syntax. To build this syntax you can use join():

set {
  name  = "app_groups"
  value = "{${join(",", local.app_groups)}}"
}

This should do the trick and provide app_groups as an array in the form of {bigquery-team, devops-team}. I am not sure if quoting is needed, but this could be added easily.