fix for import using :label instead of 'label' for some custom fields

[dnoneill]

closes #2983

What I found with this is when update runs for the license field, it makes the config :label => 'License' not 'label' => 'License'. I checked the data. It looks exactly the same as all the other fields.

[corylown]

This could use a test to show how we're handling either symbols or strings for addressing the label.

@dnoneill I think this partially addresses #2983. It definitely fixes the indexing/import error "undefined method 'downcase' for nil:NilClass". I'm still seeing a problem where the imported SolrDocumentSidecar isn't getting attached to the right resources. In the imported exhibit I end up with two sidecars and one isn't associated with the right resource for this exhibit:

[#<Spotlight::Resources::IiifHarvester:0x000000010d2c8d38
  id: 19,
  exhibit_id: 15,
  type: "Spotlight::Resources::IiifHarvester",
  url: "https://purl.stanford.edu/bb112zx3193/iiif/manifes...",
  data: {},
  indexed_at: nil,
  created_at: "2024-10-22 11:20:04.366000000 -0700",
  updated_at: "2024-10-22 11:20:04.366000000 -0700",
  metadata: nil,
  index_status: nil,
  upload_id: nil>]
exhibits(dev)> Spotlight::SolrDocumentSidecar.where(exhibit_id: '15')
  Spotlight::SolrDocumentSidecar Load (0.6ms)  SELECT "spotlight_solr_document_sidecars".* FROM "spotlight_solr_document_sidecars" WHERE "spotlight_solr_document_sidecars"."exhibit_id" = ? /* loading for pp */ LIMIT ?  [["exhibit_id", 15], ["LIMIT", 11]]
=> 
[#<Spotlight::SolrDocumentSidecar:0x000000011d4420a0
  id: 32,
  exhibit_id: 15,
  public: true,
  data: {:"iiif-test"=>"iiif test value"},
  created_at: "2024-10-22 11:20:04.909000000 -0700",
  updated_at: "2024-10-22 11:21:20.403000000 -0700",
  document_id: "e452aca00faef95351dbf0e5e37b0241",
  document_type: "SolrDocument",
  resource_id: 16,
  resource_type: nil,
  index_status: {},
  tag_list: nil>,
 #<Spotlight::SolrDocumentSidecar:0x000000011d441f60
  id: 33,
  exhibit_id: 15,
  public: true,
  data:
   {"readonly_available-online_tesim"=>["https://purl.stanford.edu/bb112zx3193"], "readonly_title_tesim"=>["Bugatti Type 51A. Road &amp; Track Salon January 1957"], "readonly_contributor_tesim"=>["Hearst Magazines, Inc. (former ownerfmo)", "Chesebrough, Jerry (photographerpht)"], "readonly_type_tesim"=>["Photographic prints", "StillImage"], "readonly_format_tesim"=>["1 folder", "image/tiff"], "readonly_language_tesim"=>["Englisheng"], "readonly_description_tesim"=>["Black and white photographic prints of the Bugatti Type 51A, used in issues of Road and Track magazine between 1957 and 1961."], "readonly_subject_tesim"=>["Bugatti", "Bugatti T51A", "Bugatti automobile"], "readonly_date_tesim"=>["1957-1961"], "readonly_identifier_tesim"=>["M1919_b129_f02", "https://purl.stanford.edu/bb112zx3193"], "readonly_relation_tesim"=>["Stanford University. Libraries. Department of Special Collections and University Archives", "Road &amp; Track magazine records, circa 1947-2012"], "readonly_publishdate_tesim"=>["2024-05-08T06:40:12Z"], "readonly_attribution_tesim"=>["Provided by the Stanford University Libraries"]},
  created_at: "2024-10-22 12:37:44.833952000 -0700",
  updated_at: "2024-10-22 12:37:44.842736000 -0700",
  document_id: "caf2778df19f8b7f05411227b7b0504a",
  document_type: "SolrDocument",
  resource_id: 19,
  resource_type: nil,
  index_status: {},
  tag_list: nil>]

Whereas in the original exhibit I exported the data looked like:

exhibits(dev)> Spotlight::Resource.where(exhibit_id: '12')
  Spotlight::Resource Load (0.5ms)  SELECT "spotlight_resources".* FROM "spotlight_resources" WHERE "spotlight_resources"."exhibit_id" = ? /* loading for pp */ LIMIT ?  [["exhibit_id", 12], ["LIMIT", 11]]
=> 
[#<Spotlight::Resources::IiifHarvester:0x000000011d4461a0
  id: 16,
  exhibit_id: 12,
  type: "Spotlight::Resources::IiifHarvester",
  url: "https://purl.stanford.edu/bb112zx3193/iiif/manifes...",
  data: {},
  indexed_at: nil,
  created_at: "2024-10-22 11:20:04.366690000 -0700",
  updated_at: "2024-10-22 11:20:04.366690000 -0700",
  metadata: nil,
  index_status: nil,
  upload_id: nil>]
exhibits(dev)> Spotlight::SolrDocumentSidecar.where(exhibit_id: '12')
  Spotlight::SolrDocumentSidecar Load (0.3ms)  SELECT "spotlight_solr_document_sidecars".* FROM "spotlight_solr_document_sidecars" WHERE "spotlight_solr_document_sidecars"."exhibit_id" = ? /* loading for pp */ LIMIT ?  [["exhibit_id", 12], ["LIMIT", 11]]
=> 
[#<Spotlight::SolrDocumentSidecar:0x000000010c97eb10
  id: 27,
  exhibit_id: 12,
  public: true,
  data: {"iiif-test"=>"iiif test value"},
  created_at: "2024-10-22 11:20:04.909936000 -0700",
  updated_at: "2024-10-22 11:21:20.403167000 -0700",
  document_id: "e452aca00faef95351dbf0e5e37b0241",
  document_type: "SolrDocument",
  resource_id: 16,
  resource_type: nil,
  index_status: {},
  tag_list: nil>]

It seems fine to me to deal with this separately, but this PR does not fully close #2983