crossref: database search fix
- Adds an instance wide search parameter prefix to perform the database search.
- NOTE for the search to be performed in the database, the DOI field prefix for the corresponding instance config file should be added (e.g. CROSSREF_SEARCH_PREFIX = 'doi:').
Signed-off-by: Pedro Gaudêncio <pedro.gaudencio@cern.ch>
Co-authored-by: Jiri Kuncar <jiri.kuncar@cern.ch>