Allow user to filter epics by reaction emoji

- backend only

changelogs/unreleased/325630-cablett-filter-epics-by-reaction-be.yml

+---
+title: Allow user to filter epics by their reaction emoji via GraphQL
+merge_request: 58211
+author:
+type: added

ee/app/graphql/resolvers/epics_resolver.rb

@@ -50,6 +50,10 @@ module Resolvers
              required: false,
              description: 'Filter epics by given confidentiality.'
 
+    argument :my_reaction_emoji, GraphQL::STRING_TYPE,
+             required: false,
+             description: 'Filter by reaction emoji applied by the current user.'
+
     type Types::EpicType, null: true
 
     def ready?(**args)

ee/spec/graphql/resolvers/epics_resolver_spec.rb

@@ -134,6 +134,17 @@ RSpec.describe Resolvers::EpicsResolver do
         end
       end
 
+      context 'with my_reaction_emoji' do
+        it 'filters epics by reaction emoji' do
+          create(:award_emoji, name: 'man_in_business_suit_levitating', user: current_user, awardable: epic1)
+          create(:award_emoji, name: 'thumbsdown', user: current_user, awardable: epic2)
+
+          epics = resolve_epics(my_reaction_emoji: 'man_in_business_suit_levitating')
+
+          expect(epics).to contain_exactly(epic1)
+        end
+      end
+
       context 'with milestone_title' do
         let_it_be(:milestone1) { create(:milestone, group: group) }