Generate Ecto embedded schemas from the XSDs cached under priv/xsd/.
mix uof.xsd.fetch # download the XSDs first (pinned SDK tag)
mix uof.gen.schemas # then generateReads the (git-ignored) priv/xsd/ cache populated by mix uof.xsd.fetch
and raises if a group's XSDs are missing. One module per complexType is
generated per group into lib/uof/api/schemas/<group>/.