queries for roles have been built

Users often want to know which time series/stations have been provided from which resource/contributor/PI, ...
Therefore, a filter should be available to make such requests.
search should consequently work on, e.g.

?roles=ResourceProvider:Umweltbundesamt,PrincipalInvestigator:example@example.com

organisations should be given by their long names, persons should be given by their email addresses.