Capture more errors in LoadUrnsJob to avoid "false positive" harvest reporting

[bkiahstroud]

Ref https://github.com/harvard-lts/CURIOSity/issues/215

Summary

There was a small section in the harvest logic where errors were not being captured and handled. If an error was thrown somewhere in this section, it would cause the initial PerformHarvestsJob to fail. This failed job would then retry itself several times, failing silently all the way. And because the errors weren't being captured, no information would be visible to the user looking in modal in the "Recent indexing activity" section of the Exhibit Dashboard.

This PR includes two key changes:

1. Capture the error

Capturing the error prevents the job from retrying itself over and over. This frees up the background working to work on other processes.

2. Handle the error

Handling the error means bubbling it up to the user, specifically in the harvest status modal. This lets the user know 1) something went wrong and 2) possibly what they can do about it.

Screenshots

Before

After

Testing Instructions

Please refer to the ticket.

[phil-plencner-hl]

This works as described.

I also updated the version of the gem to 3.0.0.pre.beta.10 so that we can deploy this to CURIOSity.

Approved.