Extract EE specific files/lines for Discussion lib/api

We have the following files containing EE specific code. We should move them to ee/

lib/api/discussions.rb

diff --git a/lib/api/discussions.rb b/home/yorickpeterse/Projects/gitlab/gdk-ee/gitlab/lib/api/discussions.rb
index 91eb6a23701..48440a7d218 100644
--- a/lib/api/discussions.rb
+++ b/home/yorickpeterse/Projects/gitlab/gdk-ee/gitlab/lib/api/discussions.rb
@@ -7,7 +7,7 @@ module API
 
     before { authenticate! }
 
-    NOTEABLE_TYPES = [Issue, Snippet, MergeRequest, Commit].freeze
+    NOTEABLE_TYPES = [Issue, Snippet, Epic, MergeRequest, Commit].freeze
 
     NOTEABLE_TYPES.each do |noteable_type|
       parent_type = noteable_type.parent_class.to_s.underscore

lib/api/group_boards.rb

diff --git a/lib/api/group_boards.rb b/home/yorickpeterse/Projects/gitlab/gdk-ee/gitlab/lib/api/group_boards.rb
index 9a20ee8c8b9..69cf0c32d0d 100644
--- a/lib/api/group_boards.rb
+++ b/home/yorickpeterse/Projects/gitlab/gdk-ee/gitlab/lib/api/group_boards.rb
@@ -5,6 +5,8 @@ module API
     include BoardsResponses
     include PaginationParams
 
+    prepend EE::API::BoardsResponses # rubocop: disable Cop/InjectEnterpriseEditionModule
+
     before do
       authenticate!
     end
@@ -22,7 +24,7 @@ module API
     resource :groups, requirements: API::NAMESPACE_OR_PROJECT_REQUIREMENTS do
       segment ':id/boards' do
         desc 'Find a group board' do
-          detail 'This feature was introduced in 10.6'
+          detail 'This feature was introduced in 10.4'
           success ::API::Entities::Board
         end
         get '/:board_id' do
@@ -30,7 +32,7 @@ module API
         end
 
         desc 'Get all group boards' do
-          detail 'This feature was introduced in 10.6'
+          detail 'This feature was introduced in 10.4'
           success Entities::Board
         end
         params do
@@ -46,7 +48,7 @@ module API
       end
       segment ':id/boards/:board_id' do
         desc 'Get the lists of a group board' do
-          detail 'Does not include backlog and closed lists. This feature was introduced in 10.6'
+          detail 'Does not include backlog and closed lists. This feature was introduced in 10.4'
           success Entities::List
         end
         params do
@@ -57,7 +59,7 @@ module API
         end
 
         desc 'Get a list of a group board' do
-          detail 'This feature was introduced in 10.6'
+          detail 'This feature was introduced in 10.4'
           success Entities::List
         end
         params do
@@ -68,7 +70,7 @@ module API
         end
 
         desc 'Create a new board list' do
-          detail 'This feature was introduced in 10.6'
+          detail 'This feature was introduced in 10.4'
           success Entities::List
         end
         params do
@@ -83,7 +85,7 @@ module API
         end
 
         desc 'Moves a board list to a new position' do
-          detail 'This feature was introduced in 10.6'
+          detail 'This feature was introduced in 10.4'
           success Entities::List
         end
         params do
@@ -99,7 +101,7 @@ module API
         end
 
         desc 'Delete a board list' do
-          detail 'This feature was introduced in 10.6'
+          detail 'This feature was introduced in 10.4'
           success Entities::List
         end
         params do

lib/api/issues.rb

diff --git a/lib/api/issues.rb b/home/yorickpeterse/Projects/gitlab/gdk-ee/gitlab/lib/api/issues.rb
index 94ed9ac6fb1..3acee1841a8 100644
--- a/lib/api/issues.rb
+++ b/home/yorickpeterse/Projects/gitlab/gdk-ee/gitlab/lib/api/issues.rb
@@ -17,6 +17,8 @@ module API
       end
     end
 
+    prepend EE::API::Issues # rubocop: disable Cop/InjectEnterpriseEditionModule
+
     helpers do
       # rubocop: disable CodeReuse/ActiveRecord
       def find_issues(args = {})
@@ -54,6 +56,7 @@ module API
         optional :scope, type: String, values: %w[created-by-me assigned-to-me created_by_me assigned_to_me all],
                          desc: 'Return issues for the given scope: `created_by_me`, `assigned_to_me` or `all`'
         optional :my_reaction_emoji, type: String, desc: 'Return issues reacted by the authenticated user by the given emoji'
+        optional :confidential, type: Boolean, desc: 'Filter confidential or public issues'
         use :pagination
 
         use :issues_params_ee
@@ -218,8 +221,9 @@ module API
                               desc: 'Date time when the issue was updated. Available only for admins and project owners.'
         optional :state_event, type: String, values: %w[reopen close], desc: 'State of the issue'
         use :issue_params
-        at_least_one_of :title, :description, :assignee_ids, :assignee_id, :milestone_id, :discussion_locked,
-                        :labels, :created_at, :due_date, :confidential, :state_event
+        at_least_one_of :title, :description, :assignee_ids, :assignee_id, :milestone_id,
+                        :labels, :created_at, :due_date, :confidential, :state_event,
+                        :weight, :discussion_locked
       end
       # rubocop: disable CodeReuse/ActiveRecord
       put ':id/issues/:issue_iid' do

lib/api/notes.rb

diff --git a/lib/api/notes.rb b/home/yorickpeterse/Projects/gitlab/gdk-ee/gitlab/lib/api/notes.rb
index f7bd092ce50..675f6b2c269 100644
--- a/lib/api/notes.rb
+++ b/home/yorickpeterse/Projects/gitlab/gdk-ee/gitlab/lib/api/notes.rb
@@ -7,7 +7,7 @@ module API
 
     before { authenticate! }
 
-    NOTEABLE_TYPES = [Issue, MergeRequest, Snippet].freeze
+    NOTEABLE_TYPES = [Issue, MergeRequest, Snippet, Epic].freeze
 
     NOTEABLE_TYPES.each do |noteable_type|
       parent_type = noteable_type.parent_class.to_s.underscore