Submission exports: complex datastructures (XML)

[sergei-maertens]

From #2305 and related to #2375

Python datastructures are now naively converted to XML nodes, mirroring the internal data structures. This makes it so we can't make backwards incompatible changes in our internal datastructures as downstream systems may rely on this

• File: single vs. multiple results in the same list-serialization and the entire datastructure is exposed while only the file name reference should be sufficient
• Map coordinates now results in two value elements, while the coordinate itself is rather a single value composed of multiple primitives.
• Additionally - while files are referenced in the exports, they are not actually included. Should we export to a ZIP with a metadata file (CSV/XML/...) and include a directory with all the referenced attachments?
• Repeating groups: it looks like only the last element of a repeating group is included rather than all items

Proposal:

• include component type for a field as an attribute
• include multiple boolean for a field as an attribute

[joeribekker]

Initial assessment: No real world reports on this but I agree we need to tackle this someday.