make _type in schema indicate the schemas type

instead of indicating that the described resource has something
called "_type"

config/locales/de.yml

@@ -1676,7 +1676,6 @@ de:
 
   api_v3:
     attributes:
-        _type: "Ressourcenart"
         lock_version: "Sperrversion"
     errors:
       code_401: "Sie müssen sich authentifizieren, um auf die Ressource zugreifen zu können."

config/locales/en.yml

@@ -1667,7 +1667,6 @@ en:
 
   api_v3:
     attributes:
-      _type: "Resource Type"
       lock_version: "Lock Version"
     errors:
       code_401: "You need to be authenticated to access this resource."

doc/apiv3-documentation.apib

@@ -767,7 +767,7 @@ contain a default value for that property. Nevertheless the client will also rec
 The content of this element *can* be used as a template for the request body of a call to **validate** or **commit**.
 
 A call to **validate** and **commit** does not need to include all properties that were defined in the `payload` section.
-It is only necessary to include the properties that you want to change, as well as the `_type` and a `lockVersion` if one is present.
+It is only necessary to include the properties that you want to change, as well as the `lockVersion` if one is present.
 However you *may* include all the properties sent in the `payload` section.
 
 ### Schema
@@ -830,10 +830,6 @@ That is because the main purpose of a form is helping the client to sort out val
                             "type": "Integer",
                             "writable": false
                         },
-                        "_type": {
-                            "type": "MetaType",
-                            "writable": false
-                        },
                         "subject": {
                             "type": "String",
                             "minLength": 1,
@@ -1608,6 +1604,7 @@ Note that regular expressions used in the API follow the rules of [Ruby Regular
     + Body
 
             {
+                "_type": "Schema",
                 "_links": {
                     "self": { "href": "/api/v3/example/schema" }
                 },
@@ -1617,11 +1614,6 @@ Note that regular expressions used in the API follow the rules of [Ruby Regular
                     "type": "Integer",
                     "writable": false
                 },
-                "_type": {
-                    "name": "Resource Type",
-                    "type": "MetaType",
-                    "writable": false
-                },
                 "subject": {
                     "name": "Subject",
                     "type": "String",
@@ -2767,10 +2759,8 @@ the human readable name of custom fields.*
 When calling this endpoint the client provides a single object, containing the properties and links that it wants to change, in the body.
 Note that it is only allowed to provide properties or links supporting the **write** operation.
 
-Additionally to the fields the client wants to change, it is mandatory to provide:
-
-* The `_type` which should as of now always be `WorkPackage`
-* The value of `lockVersion` which was received by the `GET` request this change originates from
+Additionally to the fields the client wants to change, it is mandatory to provide the value of `lockVersion` which was received
+by the `GET` request this change originates from.
 
 The value of `lockVersion` is used to implement [optimistic locking](http://en.wikipedia.org/wiki/Optimistic_concurrency_control).
 
@@ -2784,7 +2774,6 @@ The value of `lockVersion` is used to implement [optimistic locking](http://en.w
 + Request (application/json)
 
         {
-            "_type": "WorkPackage",
             "lockVersion": 13,
             "subject": "Lorem"
             "parentId": "42"

lib/api/decorators/schema.rb

@@ -142,6 +142,10 @@ module API
           self.class.represented_class.human_attribute_name(object)
         end
       end
+
+      def _type
+        'Schema'
+      end
     end
   end
 end

lib/api/v3/work_packages/form/work_package_payload_representer.rb

@@ -120,10 +120,6 @@ module API
           property :updated_at,
                    getter: -> (*) { nil }, render_nil: false
 
-          def _type
-            'WorkPackage'
-          end
-
           private
 
           def datetime_formatter

lib/api/v3/work_packages/schema/work_package_schema_representer.rb

@@ -59,11 +59,6 @@ module API
             end
           end
 
-          schema :_type,
-                 type: 'MetaType',
-                 name_source: -> (*) { I18n.t('api_v3.attributes._type') },
-                 writable: false
-
           schema :lock_version,
                  type: 'Integer',
                  name_source: -> (*) { I18n.t('api_v3.attributes.lock_version') },
@@ -194,10 +189,6 @@ module API
           def current_user
             context[:current_user]
           end
-
-          def _type
-            'MetaType'
-          end
         end
       end
     end

spec/lib/api/v3/work_packages/form/work_package_payload_representer_spec.rb

@@ -43,8 +43,6 @@ describe ::API::V3::WorkPackages::Form::WorkPackagePayloadRepresenter do
   context 'generation' do
     subject(:generated) { representer.to_json }
 
-    it { is_expected.to include_json('WorkPackage'.to_json).at_path('_type') }
-
     describe 'work_package' do
       it { is_expected.to have_json_path('subject') }
 

spec/lib/api/v3/work_packages/work_package_schema_representer_spec.rb

@@ -50,12 +50,8 @@ describe ::API::V3::WorkPackages::Schema::WorkPackageSchemaRepresenter do
     subject(:generated) { representer.to_json }
 
     describe '_type' do
-      it_behaves_like 'has basic schema properties' do
-        let(:path) { '_type' }
-        let(:type) { 'MetaType' }
-        let(:name) { I18n.t('api_v3.attributes._type') }
-        let(:required) { true }
-        let(:writable) { false }
+      it 'is indicated as Schema' do
+        is_expected.to be_json_eql('Schema'.to_json).at_path('_type')
       end
     end