XML errors in BiogHists on Export

[deternitydx]

We need to validate the XML an editor types into the biogHist when they go to submit. It is possible for a user to have updated a biogHist, made the XML invalid, and therefore cause errors on exporting to EAC-CPF XML.

Example: https://snaccooperative.org/download/83608741?type=constellation_json
This biogHist starts with the </biogHist> tag, which causes anything that parses the XML to fail.