gitlab_release resource double quotes "milestones"

Bug Report

milestones attribute double-quotes string values in API request.

Sending the following cURL works:

curl --header "PRIVATE-TOKEN: $TOKEN" \
  --header "Content-Type: application/json" \
  --request POST "https://gitlab.com/api/v4/projects/<ID>/releases" \
  --data '{"tag_name":"test","ref":"main","name":"test","description":"test","milestones":["Sprint 1","Sprint 2"]}'
# Returns 201 with milestones correctly attached

Relevant Terraform Configuration

Create milestones: "Sprint 1", "Sprint 2" in gui, run the following

resource "gitlab_release" "test" {
  project     = "<project_id>"
  tag_name    = "v1.0.0"
  name        = "v1.0.0"
  description = "test"
  ref         = "main"
  milestones  = ["Sprint 1", "Sprint 2"]
}

Relevant Terraform Command

terraform apply

Relevant Log Output

tf_http_req_body="{"milestones":["\"Sprint 1\"","\"Sprint 2\""]}"

Additional Details

• GitLab Terraform Provider Version: `17.10.0, 18.6.0, 18.6.2`
• GitLab Instance Version: `Current from gitlab.com`
• Terraform Version: `OpenTofu v1.11.5
  on linux_amd64 \
  • provider registry.opentofu.org/gitlabhq/gitlab v18.8.2
    `
• License Tier: Free