Start debugging guide for Uberon developers

[matentzn]

And add stuff like @gouttegd s perls of wisdom

While I am here, note to my future self and to anyone attempting to debug unsatisfiability issues in composite-metazoan (or any other composite-* product):

1. Don’t.
2. But if you must, then: avoid using composite-metazoan.owl itself or its direct precursor $(TMPDIR)/unreasoned-composite-metazoan.owl to chase down the cause(s) of an unsatisfiability issue. This is because the --merge-species-ontology and --merge-equivalence-sets step that are at the core of the composite pipeline may materialise axioms that were not explicitly asserted in any of the source ontologies and by doing that, it may make it impossible for any reasoner to explain to you the real root cause for an erroneous inferred assertion. Use instead an intermediate file that is just upstream of that step, $(TMPDIR)/merged-composite-metazoan.owl.

Originally posted by @gouttegd in https://github.com/obophenotype/uberon/issues/3099#issuecomment-1780682531