Guard agains incomplete related_dois (#1069)

## Purpose
Some related_identifiers do not have all the required fields in the database due to changes inthe schema.

closes: #1066, #1067, #1068

## Approach
Make sure all related_identifiers is a hash and has all the required fields

## Types of changes

- [x] Bug fix (non-breaking change which fixes an issue)

- [ ] New feature (non-breaking change which adds functionality)

- [ ] Breaking change (fix or feature that would cause existing functionality to change)

## Reviewer, please remember our [guidelines](https://datacite.atlassian.net/wiki/spaces/TEC/pages/1168375809/Pull+Request+Guidelines):

- Be humble in the language and feedback you give, ask don't tell.
- Consider using positive language as opposed to neutral when offering feedback. This is to avoid the negative bias that can occur with neutral language appearing negative.
- Offer suggestions on how to improve code e.g. simplification or expanding clarity.
- Ensure you give reasons for the changes you are proposing.

app/models/doi/indexer/related_doi_indexer.rb

@@ -2,13 +2,27 @@
 
 module Doi::Indexer
   class RelatedDoiIndexer
+    REQUIRED_KEYS = %w[
+      relatedIdentifier
+      relatedIdentifierType
+      relationType
+    ]
+
     def initialize(related_identifiers)
       @related_identifiers = Array.wrap(related_identifiers)
       @related_dois = nil
     end
 
+    def is_related_doi?(related)
+      related.is_a?(Hash) &&
+        REQUIRED_KEYS.all? { |k| related.key?(k) } &&
+        related.fetch("relatedIdentifierType", nil) == "DOI"
+    end
+
     def related_dois
-      @related_dois ||= @related_identifiers.select { |r| r.fetch("relatedIdentifierType", nil) == "DOI" }
+      @related_dois ||= @related_identifiers.select do |r|
+        is_related_doi?(r)
+      end
     end
 
     def related_grouped_by_id

spec/models/doi/related_doi_indexer_spec.rb

@@ -0,0 +1,118 @@
+
+# frozen_string_literal: true
+
+require "rails_helper"
+
+RSpec.describe Doi::Indexer::RelatedDoiIndexer do
+  describe "related_dois with different input" do
+    let(:good_related_identifier) do
+      {
+        "relatedIdentifier": "10.1234/5678",
+        "relatedIdentifierType": "DOI",
+        "relationType": "IsPartOf",
+      }.with_indifferent_access
+    end
+
+    it "handles nil input" do
+      expect(described_class.new(nil).related_dois).to eq([])
+    end
+
+    it "handles empty_string input" do
+      expect(described_class.new("").related_dois).to eq([])
+    end
+
+    it "handles a list with empty_string as input" do
+      expect(described_class.new([""]).related_dois).to eq([])
+    end
+
+
+    it "handles array of hashes with all required keys" do
+      expect(described_class.new([good_related_identifier]).related_dois).to eq(
+        [good_related_identifier])
+    end
+
+    it "handles single hash with all required keys" do
+      expect(described_class.new(good_related_identifier).related_dois).to eq(
+        [good_related_identifier])
+    end
+
+    it "exclude DOIs with if a required key is missing" do
+      expect(described_class.new(
+        good_related_identifier.except("relatedIdentifier")
+      ).related_dois).to eq([])
+      expect(described_class.new(
+        good_related_identifier.except("relatedIdentifierType")
+      ).related_dois).to eq([])
+      expect(described_class.new(
+        good_related_identifier.except("relationType")
+      ).related_dois).to eq([])
+    end
+  end
+
+  describe "relation_type grouping" do
+    let(:related_identifiers) do
+      [
+        {
+          "relatedIdentifier": "10.1234/5678",
+          "relatedIdentifierType": "DOI",
+          "relationType": "IsPartOf",
+          "resourceTypeGeneral": "Dataset",
+        }.with_indifferent_access,
+        {
+          "relatedIdentifier": "10.1234/9999",
+          "relatedIdentifierType": "DOI",
+          "relationType": "HasVersion",
+          "resourceTypeGeneral": "Text",
+        }.with_indifferent_access,
+        {
+          "relatedIdentifier": "10.1234/9999",
+          "relatedIdentifierType": "DOI",
+          "relationType": "References",
+          "resourceTypeGeneral": "Text",
+        }.with_indifferent_access
+      ]
+    end
+
+    it "can accept an array of valid identifiers" do
+      expect(described_class.new(related_identifiers).related_dois).to eq(related_identifiers)
+    end
+
+    it "groups related_dois by relatedIdentifier" do
+      expect(described_class.new(related_identifiers).relation_types_gouped_by_id).to eq(
+        {
+          "10.1234/5678" => ["is_part_of"],
+          "10.1234/9999" => ["has_version", "references"],
+        }
+      )
+    end
+
+    it "groups related_dois by relatedIdentifier" do
+      expect(described_class.new(related_identifiers).related_grouped_by_id).to eq(
+        {
+          "10.1234/5678" => [
+            {
+              "relatedIdentifier" => "10.1234/5678",
+              "relatedIdentifierType" => "DOI",
+              "relationType" => "IsPartOf",
+              "resourceTypeGeneral" => "Dataset",
+            }
+          ],
+          "10.1234/9999" => [
+            {
+              "relatedIdentifier" => "10.1234/9999",
+              "relatedIdentifierType" => "DOI",
+              "relationType" => "HasVersion",
+              "resourceTypeGeneral" => "Text",
+            },
+            {
+              "relatedIdentifier" => "10.1234/9999",
+              "relatedIdentifierType" => "DOI",
+              "relationType" => "References",
+              "resourceTypeGeneral" => "Text",
+            }
+          ],
+        }
+      )
+    end
+  end
+end