composite sources

[annamorphism]

Today in meeting we discussed having composite sources. For example, at the moment we have some fragments that are probably originally from the same source, but you have to look at each of them separately. (https://cantusdatabase.org/source/706887 and https://cantusdatabase.org/source/698356 form a pair; so do http://cantus.uwaterloo.ca/source/699214 and
https://cantusdatabase.org/source/697918; and https://cantusdatabase.org/source/701224 and http://cantusdatabase.org/source/701386 are in fact different parts of the same page.) It would be very cool to one day be able to, say, attach these sources into one composite source, or maybe have a chant be attached to both a fragment-sources and a set-of-fragments source. (We also have a set-of-fragments source already, https://cantusdatabase.org/source/123609, but none of the constituent fragments is a source in its own right.)
Note that you would sometimes want to re-order things at the folio level, so it's not as simple as saying is followed by --the contents might be interspersed in some way.