OPSMN-4588: Check whether the text after the last dot in the filename is one of the recognised file extension. If not, automatically append '.csv' extension to the filename.
OPSMN-4588: Check whether the text after the last dot in the filename is one of
the recognised file extension. If not, automatically append '.csv' extension
to the filename.

The recognised extensions are - csv, css, doc, docx, html, jar,
java, js, json, pdf, txt, xls, xlsx, xml, zip

krishagni/openspecimen,krishagni/openspecimen,krishagni/openspecimen