{% comment %}
Renders a single EXTRA (non-canonical) register field — promo/ref/tracking/etc.
Driven by auth_config.registration.extra_fields via
register_schema.resolve_extra_fields(); see register_schema.py.

Visible fields are hidden initially: page_script reveals the input when there
is no matching URL query param, or pre-sets its value (still hidden) when there
is. Capture-only fields intentionally emit no editable DOM at all; page_script
collects their matching query parameter from the server-sanitized value map.

Input context:
    ef.name      — the extra field name (e.g. "promo")
    ef.label     — display label / placeholder
    ef.required  — bool (client-side UX hint only; server keeps the
                   silent-drop contract for extras)
    ef.capture_only — bool; omit the row/input when true
    ef.help_text — optional accessible guidance for visible inputs
{% endcomment %}
{% if not ef.capture_only %}
<div class="mat-field" id="reg-extra-row-{{ ef.name }}" style="display:none">
    <label class="mat-label" for="reg-extra-{{ ef.name }}">{{ ef.label }}</label>
    <input class="mat-input" type="text" id="reg-extra-{{ ef.name }}" autocomplete="off" maxlength="{{ register_extra_value_max_length|default:512 }}" placeholder="{{ ef.label }}"{% if ef.required %} data-required="1"{% endif %}{% if ef.help_text %} aria-describedby="reg-extra-help-{{ ef.name }}"{% endif %} />
    {% if ef.help_text %}<p class="mat-field-help" id="reg-extra-help-{{ ef.name }}">{{ ef.help_text }}</p>{% endif %}
</div>
{% endif %}