12685 use markdown for custom fields added to form

[arthanson]

Fixes: #12685

Renders custom field description (for help text) using markdown for forms. Did the escape first so it catches html and just process markdown afterwards.

[kkthxbye-code]

This does not match the markdown supported elsewhere in netbox. Easiest way to demonstrate is to set the description to <strong>test</strong>.

How it's displayed in different parts of the UI:

Custom field object view:

Target object view:

Target object edit view:

All other places we render markdown is done with from utilities.templatetags.builtins.filters import render_markdown.

When setting the description to **test** the custom field object view and the target object edit view works, but not the target object view:

Custom field object view:

Target object view:

Target object edit view:

The cause is that the PR doesn't modify this:

netbox/netbox/templates/inc/panels/custom_fields.html

Lines 19 to 22 in 69215c4

	class="mdi mdi-information text-primary"
	data-bs-toggle="tooltip"
	data-bs-placement="right"
	title="{{ field.description|escape }}"