How to remove trailing commas

A common problem when generating JSON in a loop is the trailing comma, which is invalid JSON.

To avoid the trailing comma in loops, use if not loop.last provided by Tera.

example.tera

---
whiskers:
  version: "^X.Y.Z"
---
{
  "themes": [
    {%- for id, flavor in flavors %}
    {
      "id": "catppuccin-{{id}}",
    }{% if not loop.last %},{% endif %}
    {%- endfor %}
  ]
}