OAIHarvest: fix identifier parsing
- Fixes the identifier parsing that was too happy about adding arXiv prefix to identifiers specified via CLI or web interface when harvesting. (PR #2408)
- Adds tests for the identifier parsing.
Reported-by: Sebastian Witowski <sebastian.witowski@cern.ch>
Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>