Accurately reflect disk-quota in manifest diffs

We accept both `disk-quota` (older style) and `disk_quota` (preferred),
but they refer to the same value, so that should be reflected in the
diff

[Finishes #174872722]

Co-authored-by: Chris Selzo <cselzo@pivotal.io>
Co-authored-by: Teal Stannard <tstannard@pivotal.io>

Author: selzoc

app/actions/space_diff_manifest.rb

@@ -75,6 +75,12 @@ def self.generate_diff(app_manifests, space)
           existing_app_hash = manifest_presenter.to_hash.deep_stringify_keys['applications'][0]
           web_process_hash = existing_app_hash['processes'].find { |p| p['type'] == 'web' }
           existing_app_hash = existing_app_hash.merge(web_process_hash) if web_process_hash
+
+          # Account for the fact that older manifests may have a hyphen for disk-quota
+          if manifest_app_hash.key?('disk-quota')
+            existing_app_hash['disk-quota'] = existing_app_hash['disk_quota']
+            recognized_top_level_keys << 'disk-quota'
+          end
         end
 
         manifest_app_hash.each do |key, value|

spec/request/space_manifests_spec.rb

@@ -516,6 +516,7 @@
         {
           diff: a_collection_containing_exactly(
             { op: 'replace', path: '/applications/0/memory', was: '1024M', value: '256M' },
+            { op: 'replace', path: '/applications/0/disk-quota', was: '1024M', value: '2G' },
           )
         }
       end
@@ -525,7 +526,8 @@
           'applications' => [
             {
               'name' => app1_model.name,
-              'memory' => '256M'
+              'memory' => '256M',
+              'disk-quota' => '2G',
             }
           ]
         }.to_yaml