Add group membership management with role-based access control

[Copilot]

Module now supports managing GitLab group members with different access levels (owner, maintainer, developer, reporter, guest).

Changes

Variables (variables.tf)

• Added members map for flexible configuration with optional expiration dates
• Added convenience lists: owners, maintainers, developers, reporters, guests
• All inputs validate user IDs (positive integers) and date formats (YYYY-MM-DD)

Resources (main.tf)

• Created gitlab_group_membership resources using for_each for each access level
• Local variables convert user ID lists to sets for efficient management

Outputs (outputs.tf)

• members: All members with access levels and expiration dates
• member_count: Total member count
• member_ids: Distinct list of user IDs

Usage

Simple lists for common use:

module "team" {
  source = "sudo-terraform-modules/groups/gitlab"
  
  name = "backend-team"
  path = "backend-team"
  
  owners      = [101, 102]
  developers  = [301, 302, 303]
}

Advanced configuration with expiration:

module "project" {
  source = "sudo-terraform-modules/groups/gitlab"
  
  name = "project-alpha"
  path = "project-alpha"
  
  owners = [100]
  members = {
    contractor = {
      user_id      = 300
      access_level = "developer"
      expires_at   = "2024-12-31"
    }
  }
}

All new variables default to empty, maintaining backwards compatibility.

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.