RunRouter filling skips whole Event if any specs are unknown

[danielballan]

The functionality of RunRouter's filling is confusing. By default, it tries to fill and silently gives up if it encounters a spec it doesn't know. You can opt in to stricter behavior. So far, so good.

event-model/event_model/__init__.py

Lines 1223 to 1227 in 14b0826

	fill_or_fail: boolean, optional
	By default (False), if a document with a spec not in
	``handler_registry`` is encountered, let it pass through unfilled. But
	if set to True, fill everything and `raise
	``UndefinedAssetSpecification`` if some unknown spec is encountered.

But when it fails to resolve a spec, it bails on filling the entire document. That is, if an Event has fields from two detectors, and we know how to fill Detector A but we don't know how to fill Detector B, neither will be filled.

I haven't given thought yet to what we should do about this, just making sure it is documented.

event-model/event_model/__init__.py

Lines 1342 to 1349 in 14b0826

	def event_page(self, doc):
	descriptor_uid = doc['descriptor']
	start_uid = self._descriptor_to_start[descriptor_uid]
	try:
	doc = self._fillers[start_uid].event_page(doc)
	except UndefinedAssetSpecification:
	if self.fill_or_fail:
	raise

[tacaswell]

I am (on 45s of thought) in favor of filling as much as we can when in forgiving mode. It gives you a nice signal of "that field is broken" ;)