Add shared GitLab user enumeration for gl users enum and gluna users enum

[Copilot]

Adds GitLab user enumeration to both authenticated and unauthenticated command trees. The new commands iterate all users exposed by the GitLab API and emit one structured zerolog entry per user, reusing a shared implementation.

• New command surface

  • Adds gl users enum
  • Adds gluna users enum
  • Wires a new users command group into both GitLab roots

• Shared enumeration logic

  • Introduces a shared GitLab users enumerator under pkg/gitlab/users
  • Walks /api/v4/users with pagination until exhaustion
  • Supports both token-backed and anonymous access through the same code path

• Logging behavior

  • Emits one structured log line per discovered user
  • Includes useful user context such as:
    • id
    • username
    • name
    • publicEmail
    • profile
    • state
    • bot
    • admin
    • external
    • privateProfile

• Command/config handling

  • Uses the standard config binding path for --gitlab / --token
  • Requires only the GitLab URL for enumeration
  • Keeps token validation conditional so gluna users enum remains tokenless

Example:

pipeleek gl users enum --gitlab https://gitlab.example.com --token glpat-xxxx
pipeleek gluna users enum --gitlab https://gitlab.example.com

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• gitlab.com
  • Triggering command: /tmp/go-build4180218215/b2288/engine.test /tmp/go-build4180218215/b2288/engine.test -test.testlogfile=/tmp/go-build4180218215/b2288/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true -dwarf=false -goversion go1.26.0 -c=4 -race -nolocalimports -importcfg -ato�� -bool t ux-amd64/pkg/tool/linux_amd64/vet -errorsas -ifaceassert t ux-amd64/pkg/too-importcfg (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)