The impl. and tests for TRN-336.

https://jira2.iparadigms.com/browse/TRN-336 reads:

I did a filter by regex: http://research-cr1.oak.iparadigms.com/links/jst.go.jp?filterRegex=FYVFYLTQMRTA====
And in the page it says: "(filtered by /FYVFYLTQMRTA====/)" where I expect it should probably say "(filtered by /.*\.pdf/)"

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There was regression in the code around this bug, looks fixed now. Test added.