Add metadata function for submission review data_type

[ivermac]

Ideally, it would be more less same as the following but now for submission review

onadata/onadata/apps/main/models/meta_data.py

Lines 254 to 257 in 7941f71

	@staticmethod
	def published_by_formbuilder(content_object, data_value=None):
	data_type = 'published_by_formbuilder'
	return unique_type_for_form(content_object, data_type, data_value)

The data_value should either be True or False

Aha! Link: https://ona.aha.io/features/PROD-266

[ukanga]

We might need to also look at the /metadata endpoint to ensure we only create one only single submission-review metadata for a form.

data_type = 'submission-review'
data_value = 'True'