Remove formatting restrictions on <instanceID> (submission UUID) strings

[jnm]

The OpenRosa spec allows people to implement a "custom ID scheme" for <instanceID>, although it "must be a universally unique string identifying this specific submission".

We don't currently support this:

kobocat/onadata/apps/logger/xform_instance_parser.py

Lines 72 to 93 in a8fbca5

	def get_uuid_from_xml(xml):
	def _uuid_only(uuid, regex):
	matches = regex.match(uuid)
	if matches and len(matches.groups()) > 0:
	return matches.groups()[0]
	return None
	uuid = get_meta_from_xml(xml, "instanceID")
	regex = re.compile(r"uuid:(.*)")
	if uuid:
	return _uuid_only(uuid, regex)
	# check in survey_node attributes
	xml = clean_and_parse_xml(xml)
	children = xml.childNodes
	# children ideally contains a single element
	# that is the parent of all survey elements
	if children.length == 0:
	raise ValueError(t("XML string must have a survey element."))
	survey_node = children[0]
	uuid = survey_node.getAttribute('instanceID')
	if uuid != '':
	return _uuid_only(uuid, regex)
	return None

Some people have uploaded submissions containing the likes of

<meta><instanceID>RYAPHKJBDOZJWQ2W5BDXQ0MLU</instanceID>…

This results in the logger_instance.uuid column diverging from the <instanceID> in the XML.

We should:

1. Enforce UUID uniqueness across the entire logger_instance table;
2. After that, remove our formatting restrictions on the <instanceID> string

[jnm]

We could enforce xml_hash uniqueness before removing the formatting restrictions, but we could not (I was mistaken) enforce UUID uniqueness while the formatting restrictions are in place. That's because we need to identify cases where UUIDs collide but XML content is not identical, and then rewrite their UUIDs to append something like "DUPLICATE n" (which would violate the existing formatting restrictions).

Some internal discussion at https://chat.kobotoolbox.org/#narrow/stream/4-Kobo-Dev/topic/Duplicated.20submission.20UUIDs/near/192516

[noliveleger]

Closed because it is gonna be handled by kobotoolbox/kpi#5047