Allow OpenURI to Redirect from HTTP to HTTPS

Production Plum redirects manifest URLs to https, which was breaking
auto-updates in Pomegranate. This allows for that behavior.

Gemfile

@@ -78,3 +78,4 @@ gem 'devise_invitable'
 gem 'iiif-presentation'
 gem 'omniauth-cas'
 gem 'sneakers'
+gem 'open_uri_redirections'

Gemfile.lock

@@ -298,6 +298,7 @@ GEM
       addressable (~> 2.3)
       nokogiri (~> 1.5)
       omniauth (~> 1.2.0)
+    open_uri_redirections (0.2.1)
     openseadragon (0.2.1)
       rails (> 3.2.0)
     orm_adapter (0.5.0)
@@ -522,6 +523,7 @@ DEPENDENCIES
   jettywrapper (>= 2.0)
   jquery-rails
   omniauth-cas
+  open_uri_redirections
   pg
   poltergeist
   pry-rails

app/models/iiif_resource.rb

@@ -1,5 +1,6 @@
 require 'iiif/presentation'
 require 'open-uri'
+require 'open_uri_redirections'
 
 class IIIFResource < Spotlight::Resource
   belongs_to :exhibit, class_name: 'Spotlight::Exhibit'
@@ -21,7 +22,7 @@ def field_name(name)
 
   def manifest
     return {} if url.blank?
-    @manifest ||= ::IIIF::Service.parse(open(url).read)
+    @manifest ||= ::IIIF::Service.parse(open(url, allow_redirections: :safe).read)
   end
 
   def to_solr

spec/models/iiif_resource_spec.rb

@@ -38,7 +38,7 @@
     let(:exhibit) { Spotlight::Exhibit.create title: 'Exhibit A' }
 
     before do
-      allow_any_instance_of(described_class).to receive(:open).with(url).and_return(StringIO.new(json))
+      allow_any_instance_of(described_class).to receive(:open).with(url, allow_redirections: :safe).and_return(StringIO.new(json))
     end
 
     describe '#initialize' do
@@ -75,7 +75,7 @@
         expect(solr_doc[:creator_ssim]).to eq(['Author, Alice, 1954-'])
         expect(solr_doc[:date_created_ssim]).to eq(['1985'])
 
-        allow_any_instance_of(described_class).to receive(:open).with(url).and_return(StringIO.new(updated_json))
+        allow_any_instance_of(described_class).to receive(:open).with(url, allow_redirections: :safe).and_return(StringIO.new(updated_json))
         subject.instance_variable_set :@manifest, nil
         updated_doc = subject.to_solr
         expect(updated_doc[:full_title_ssim]).to eq('Updated Manifest')