Exhibit-specific fields work with harvesting

[bkiahstroud]

Ref https://github.com/harvard-lts/CURIOSity/issues/170

Summary

Fixes a bug where exhibit-specific fields were not getting populated with data when harvesting.

Testing Instructions

Follow Vanessa's steps here.

Expected behavior: the exhibit-specific fields populate with data when harvesting.

Explanation

Short version

The incoming metadata was not being formatted in the way that Spotlight expects, leading to the bug. Exhibit-specific fields and default "configured" fields are now formatted as required.

Long version

I made several discoveries while troubleshooting this issue:

1. As far as I can tell, the #data in a Spotlight::Resources::OaipmhUpload has no bearing on the data that gets persisted in Solr

This is partially expected; the resource's associated sidecar's (Spotlight::SolrDocumentSidecar) #data is what goes to Solr, which is expected. But updating the resource's #data (after initial creation) does not automatically update its sidecar; instead, the sidecar's #data also has to be updated manually.

Example scenarios

Resource creation, works as expected

1. Initialize a resource with data
2. Save the resource
3. The resource's sidecar is created at save time with the resource's data 
4. The sidecar's data gets indexed into Solr

Resource update (attempt to update data in Solr through resource), does not work as expected

1. Find existing resource
2. Update resource's #data 
3. Run #save_and_index on resource 
4. Resource updated successfully 
5. Resource's sidecar doesn't change 
6. Unchanged sidecar gets indexed 
7. No data changed in Solr 

Resource update (attempt to update data in Solr through resource's sidecar), succeeds

1. Find existing resource 
2. Update resource's #data
3. Update resource's sidecar's #data
4. Run #save_and_index on resource 
5. Updated sidecar gets indexed 
6. Updated data gets persisted in Solr

This is further supported by the fact that if you edit an resource in the UI, it "works" but the resource remains unchanged; the resource's sidecar is what changes!

It feels like the resource only gets used at create time and is vestigial after that.

2. OaipmhUpload#data and SolrDocumentSidecar#data expect different formats

Example:

# Correct OaipmhUpload#data format
{
  'full_title_tesim' => 'Title',
  'custom-field' => 'Hello world'
}

# Correct SolrDocumentSidecar#data format
{
  'configured_fields' => {
    'full_title_tesim' => 'Title'
  },
  'custom-field' => 'Hello world'
}

3. Exhibit-specific fields ("custom fields" in the code) are expected to not have a Solr suffix in the #data hashes

# Bad
'custom-field_tesim'

# Good
'custom-field'

[bkiahstroud]

Refer to #1 under the "Long version" section of this PR's description for an explanation

[bkiahstroud]

Refer to #2 under the "Long version" section of this PR's description for an explanation

[bkiahstroud]

Refer to #3 under the "Long version" section of this PR's description for an explanation

[phil-plencner-hl]

Looks good. Comments on my review here:
https://github.com/harvard-lts/CURIOSity/issues/170#issuecomment-1249454314