@cpennington note here that I had to reset the `scope_ids` for _both_ the module and the descriptor, because I found in different call chains that `KvsFieldData._key` would be receiving `'xblock.core.LTIDescriptorWithMixins'` in some cases (like the PUT on the result endpoint) and the `'xblock.core.LTIModuleWithMixins'` in others (like GET to the result endpoint)