feat: Add support for `not` filter to Epics API

doc/api/epics.md

@@ -75,6 +75,7 @@ GET /groups/:id/epics?state=opened
 | `include_ancestor_groups` | boolean    | no         | Include epics from the requested group's ancestors. Default is `false`                                                      |
 | `include_descendant_groups` | boolean  | no         | Include epics from the requested group's descendants. Default is `true`                                                     |
 | `my_reaction_emoji` | string           | no         | Return epics reacted by the authenticated user by the given emoji. `None` returns epics not given a reaction. `Any` returns epics given at least one reaction. Available in [GitLab 13.0](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/31479) and later |
+| `not` | Hash | no | Return epics that do not match the parameters supplied. Accepts: `author_id` and `labels`. Available in [GitLab 14.6](https://gitlab.com/gitlab-org/gitlab/-/issues/347525) and later |
 ```shell
 curl --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/groups/1/epics"

ee/lib/api/epics.rb

@@ -13,6 +13,13 @@ class Epics < ::API::Base
     helpers ::API::Helpers::EpicsHelpers
+    helpers do
+      params :negatable_epic_filter_params do
+        optional :labels, type: Array[String], coerce_with: ::API::Validations::Types::CommaSeparatedToArray.coerce, desc: 'Comma-separated list of label names'
+        optional :author_id, type: Integer, desc: 'Return epics which are not authored by the user with the given ID'
+      end
+    end
+
     params do
       requires :id, type: String, desc: 'The ID of a group'
     end
@@ -41,6 +48,10 @@ class Epics < ::API::Base
         optional :my_reaction_emoji, type: String, desc: 'Return epics reacted by the authenticated user by the given emoji'
         optional :confidential, type: Boolean, desc: 'Return epics with given confidentiality'
         use :pagination
+
+        optional :not, type: Hash do
+          use :negatable_epic_filter_params
+        end
       end
       [':id/epics', ':id/-/epics'].each do |path|
         get path do

ee/lib/api/helpers/epics_helpers.rb

@@ -43,6 +43,8 @@ def epic
       def find_epics(finder_params: {}, preload: nil)
         args = declared_params.merge(finder_params)
         args[:label_name] = args.delete(:labels)
+        args[:not] ||= {}
+        args[:not][:label_name] ||= args[:not].delete(:labels)
         epics = EpicsFinder.new(current_user, args).execute.preload(preload)

ee/spec/requests/api/epics_spec.rb

@@ -184,6 +184,18 @@
         stub_licensed_features(epics: true)
       end
+      it 'returns epics not authored by the given author id' do
+        get api(url), params: { not: { author_id: user2.id } }
+
+        expect_paginated_array_response([epic.id])
+      end
+
+      it 'returns epics without the given label' do
+        get api(url), params: { not: { labels: label.title } }
+
+        expect_paginated_array_response([epic.id])
+      end
+
       it 'returns epics authored by the given author id' do
         get api(url), params: { author_id: user2.id }