Perhaps multival should be renamed multiValued to comply with schema lingo?
Also, if I make it (optionally) schema aware, I can set multiValued behavior as default if dest field is multivalued. Also, perhaps it makes sense to allow append for multiValued as well, and let it append all source fields to a string, and then adding this concatenated string as one single field value instead of each source as its own value?
The reason I want to be able to disable strict schema checking is in the case where a processor creates intermediate fields only, which we know will be removed from SolrInputDocument before indexing, so that we can be free to name it whatever we like without causing an error. Unfortunately, ExtractingRequestHandler is too strict here and would benefit from a enforceSchema=false option.