{% comment %} One slot cell of a row of the series table: a channel
column's, or a photometry column's, which behave alike.

Takes two context variables: `slot`, as `_make_cell` builds it, and
`kind`, `channel` or `photometry`, which names the cell's classes -- the
client reads a row's channels from its `channel-cell`s and its
photometries from its `photometry-cell`s.
{% endcomment %}
{% if slot.fixed %}
{% comment %} A column with one option is no choice at all, so the cell
   states what it binds rather than asking, and says so in `data-value`,
   which is where the client reads a settled binding from -- for a channel
   column the channel, and the photometric reference where the column
   binds one, which the text need not name but the `title` shows on hover.
{% endcomment %}
<td class="{{ kind }}-cell" data-sort="{{ slot.sort }}" data-value="{{ slot.value }}"
    {% if slot.title %}title="{{ slot.title }}"{% endif %}>
    {{ slot.label }}
</td>
{% else %}
{% comment %} Each option's `title` is its reference's path, and the
   dropdown's is the chosen one's, which the client keeps current as the
   choice changes. Empty for a photometry column, which has none.
{% endcomment %}
<td class="{{ kind }}-cell" data-sort="{{ slot.sort }}">
    <select class="{{ kind }}-select" title="{{ slot.title }}">
        {% for option in slot.options %}
        <option value="{{ option.value }}" title="{{ option.title }}"
                {% if option.value == slot.value %}selected{% endif %}>{{ option.text }}</option>
        {% endfor %}
    </select>
</td>
{% endif %}