Add ALLOW_EXTRA keys in web-api problem validation
Add ALLOW_EXTRA keys in web-api problem validation

Required when ALLOW_EXTRA is enabled for shell-manager. This enables
more permissive problem.json metadata

royragsdale/picoCTF,royragsdale/picoCTF,royragsdale/picoCTF,picoCTF/picoCTF,royragsdale/picoCTF,picoCTF/picoCTF,royragsdale/picoCTF,picoCTF/picoCTF,picoCTF/picoCTF,royragsdale/picoCTF,picoCTF/picoCTF,picoCTF/picoCTF,royragsdale/picoCTF