Fix linting issues by creating new indexes

rubocop/rubocop-rails#197 introduced a new cop to rubocop-rails that checks for unique validation on an index if it's present in the model. This caused a number of failures when upgrading to 2.5.0 that this fixes.

db/migrate/20200326094046_index_creation.rb

@@ -0,0 +1,30 @@
+class IndexCreation < ActiveRecord::Migration[5.1]
+  def change
+    remove_index :about_pages, :name if index_exists?(:about_pages, :name)
+    add_index :about_pages, :name, unique: true
+
+    remove_index :classifications, :name if index_exists?(:classifications, :name)
+    add_index :classifications, :name, unique: true
+
+    remove_index :classification_relations, :classification_id if index_exists?(:classification_relations, :classification_id)
+    add_index :classification_relations, :classification_id, unique: true
+
+    remove_index :document_collection_groups, :heading if index_exists?(:document_collection_groups, :heading)
+    add_index :document_collection_groups, :heading, unique: true
+
+    remove_index :edition_relations, :document_id if index_exists?(:edition_relations, :document_id)
+    add_index :edition_relations, :document_id, unique: true
+
+    remove_index :operational_fields, :name if index_exists?(:operational_fields, :name)
+    add_index :operational_fields, :name, unique: true
+
+    remove_index :related_mainstreams, :content_id if index_exists?(:related_mainstreams, :content_id)
+    add_index :related_mainstreams, :content_id, unique: true
+
+    remove_index :social_media_services, :name if index_exists?(:social_media_services, :name)
+    add_index :social_media_services, :name, unique: true
+
+    remove_index :specialist_sectors, :topic_content_id if index_exists?(:specialist_sectors, :topic_content_id)
+    add_index :specialist_sectors, :topic_content_id, unique: true
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20200211132528) do
+ActiveRecord::Schema.define(version: 20200326094046) do
 
   create_table "about_pages", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci" do |t|
     t.integer "topical_event_id"
@@ -21,6 +21,7 @@
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.string "content_id"
+    t.index ["name"], name: "index_about_pages_on_name", unique: true
   end
 
   create_table "access_and_opening_times", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci" do |t|
@@ -134,7 +135,7 @@
     t.integer "related_classification_id", null: false
     t.datetime "created_at"
     t.datetime "updated_at"
-    t.index ["classification_id"], name: "index_classification_relations_on_classification_id"
+    t.index ["classification_id"], name: "index_classification_relations_on_classification_id", unique: true
     t.index ["related_classification_id"], name: "index_classification_relations_on_related_classification_id"
   end
 
@@ -151,6 +152,7 @@
     t.date "start_date"
     t.date "end_date"
     t.string "content_id"
+    t.index ["name"], name: "index_classifications_on_name", unique: true
     t.index ["slug"], name: "index_classifications_on_slug"
   end
 
@@ -260,6 +262,7 @@
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.index ["document_collection_id", "ordering"], name: "index_dc_groups_on_dc_id_and_ordering"
+    t.index ["heading"], name: "index_document_collection_groups_on_heading", unique: true
   end
 
   create_table "document_collection_non_whitehall_links", force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|
@@ -333,7 +336,7 @@
     t.datetime "created_at"
     t.datetime "updated_at"
     t.integer "document_id"
-    t.index ["document_id"], name: "index_edition_relations_on_document_id"
+    t.index ["document_id"], name: "index_edition_relations_on_document_id", unique: true
     t.index ["edition_id"], name: "index_edition_relations_on_edition_id"
   end
 
@@ -697,6 +700,7 @@
     t.text "description"
     t.string "slug"
     t.string "content_id"
+    t.index ["name"], name: "index_operational_fields_on_name", unique: true
     t.index ["slug"], name: "index_operational_fields_on_slug"
   end
 
@@ -866,6 +870,7 @@
     t.boolean "additional", default: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.index ["content_id"], name: "index_related_mainstreams_on_content_id", unique: true
     t.index ["edition_id"], name: "index_related_mainstreams_on_edition_id"
   end
 
@@ -950,6 +955,7 @@
     t.string "name"
     t.datetime "created_at"
     t.datetime "updated_at"
+    t.index ["name"], name: "index_social_media_services_on_name", unique: true
   end
 
   create_table "specialist_sectors", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci" do |t|
@@ -960,6 +966,7 @@
     t.boolean "primary", default: false
     t.string "topic_content_id"
     t.index ["edition_id", "tag"], name: "index_specialist_sectors_on_edition_id_and_tag", unique: true
+    t.index ["topic_content_id"], name: "index_specialist_sectors_on_topic_content_id", unique: true
   end
 
   create_table "sponsorships", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|