Use informative user-agent for harvester

[alanorth]

OpenRXV does not currently specify a User-Agent header when it connects to DSpace for harvesting. This makes it difficult to distinguish it from legitimate clients and bad actors. Furthermore, its harvesting activity causes statistics impressions to be made for every single item, every single time it harvests, which incorrectly inflate the statistics.

By default DSpace does not register statistics hits if a user agent containing the string "bot" is used, so I suggest we use something like this:

OpenRXV harvesting bot; https://github.com/ilri/OpenRXV

[alanorth]

The string is currently axios/0.19.2. Perhaps this will help:

axios/axios#2560

I'd prefer some user agent with "bot" in the name, as those won't register statistics impressions in our system. Perhaps OpenRXV harvesting bot; https://github.com/ilri/OpenRXV, with a link so people know what it is?

[alanorth]

I confirm that this is working. Thanks!