Add publishers field to record type

Why these changes are being introduced:

We recently [made the decision in transmogrifier](MITLibraries/transmogrifier#132)
To map publication information to a new nested field, named
`publishers` to avoid a naming conflict with the existing
`publicationInformation` field.

Relevant ticket(s):

* [GDT-270](https://mitlibraries.atlassian.net/browse/GDT-270)
* [GDT-218](https://mitlibraries.atlassian.net/browse/GDT-218)
* [GDT-229](https://mitlibraries.atlassian.net/browse/GDT-229)
* [GDT-271](https://mitlibraries.atlassian.net/browse/GDT-271)

How this addresses that need:

This adds the new `publishers` field and deprecates
`publicationInformation`.

Side effects of this change:

A follow-on ticket is needed to add this field to the UI. (This
is ticketed as GDT-271.)

app/graphql/types/record_type.rb

@@ -131,6 +131,12 @@ def matched_phrases
     end
   end
 
+  class PublishersType < Types::BaseObject
+    field :name, String, description: 'The name of the publisher'
+    field :date, String, description: 'The date of the publication'
+    field :location, String, description: 'Where the publisher is located'
+  end
+
   class RecordType < Types::BaseObject
     field :identifier, ID, null: false, deprecation_reason: 'Use `timdex_record_id`'
     field :timdex_record_id, ID, null: false, description: 'TIMDEX unique identifier for the item'
@@ -158,8 +164,8 @@ class RecordType < Types::BaseObject
     field :call_numbers, [String], null: true, description: 'Identification number used to classify and locate item'
     field :citation, String, null: true, description: 'Citation for item'
     field :edition, String, null: true, description: 'Edition information for item'
-    field :imprint, [String], null: true, deprecation_reason: 'Use `publicationInformation`'
-    field :publication_information, [String], description: 'Imprint information for item'
+    field :imprint, [String], null: true, deprecation_reason: 'Use `publishers`'
+    field :publication_information, [String], deprecation_reason: 'Use `publishers`'
     field :physical_description, String, null: true, description: 'Physical description of item'
     field :publication_frequency, [String], null: true,
                                             description: 'Publication frequency of item (used for serials)'
@@ -188,6 +194,7 @@ class RecordType < Types::BaseObject
     field :provider, String,
           null: true,
           description: 'The host institution for a resource. Currently only used for geospatial records'
+    field :publishers, [Types::PublishersType], null: true, description: 'Publishers that are associated with the item'
 
     def in_bibliography
       @object['related_items']&.map { |i| i['uri'] if i['relationship'] == 'IsCitedBy' }&.compact