Add add_ssh_key audit event type

What does this MR do and why?

User audit event already existed, however, it had no event name. This MR adds the add_ssh_key audit event type and extends to a Group audit event if the user is an Enterprise User.

References

#361778 (closed)

Screenshots or screen recordings

Before	After

Before:

  {
    "id": 32,
    "author_id": 76,
    "entity_id": 76,
    "entity_type": "User",
    "event_name": null,
    "details": {
      "custom_message": "Added SSH key",
      "author_name": "Test User",
      "target_id": 16,
      "target_type": "User",
      "target_details": "SSH Key",
      "ip_address": "127.0.0.1",
      "entity_path": "test",
      "author_email": "test@test.test"
    },
    "created_at": "2025-06-23T16:51:18.317Z"
  }

After:

  {
    "id": 34,
    "author_id": 76,
    "entity_id": 76,
    "entity_type": "User",
    "event_name": "add_ssh_key",
    "details": {
      "event_name": "add_ssh_key",
      "author_name": "Test User",
      "author_class": "User",
      "target_id": 17,
      "target_type": "Key",
      "target_details": "SSH Key",
      "custom_message": "Added SSH key",
      "ip_address": "127.0.0.1",
      "entity_path": "test",
      "author_email": "test@test.test"
    },
    "created_at": "2025-06-23T16:52:13.785Z"
  }

How to set up and validate locally

1. Add an SSH key to your GitLab account
2. Review Instance audit events

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