Epic sidebar widget using Apollo [RUN AS-IF-FOSS]

...s/javascripts/boards/components/board_content_sidebar.vue

app/views/shared/issuable/_sidebar.html.haml

...s/boards/components/sidebar/board_sidebar_epic_select.vue

...avascripts/sidebar/components/sidebar_dropdown_widget.vue

ee/app/assets/javascripts/sidebar/constants.js

ee/app/assets/javascripts/sidebar/mount_sidebar.js

.../assets/javascripts/sidebar/queries/epic.fragment.graphql

...ets/javascripts/sidebar/queries/group_epics.query.graphql

...ripts/sidebar/queries/project_issue_epic.mutation.graphql

...ascripts/sidebar/queries/project_issue_epic.query.graphql

ee/app/views/shared/issuable/_sidebar_item_epic.haml

ee/spec/features/boards/sidebar_spec.rb

ee/spec/features/issues/epic_in_issue_sidebar_spec.rb

ee/spec/features/projects/issues/user_creates_issue_spec.rb

...mponents/__snapshots__/board_content_sidebar_spec.js.snap

.../frontend/boards/components/board_content_sidebar_spec.js

...ards/components/sidebar/board_sidebar_epic_select_spec.js

...ontend/sidebar/components/sidebar_dropdown_widget_spec.js

...ntend/sidebar/components/sidebar_iteration_widget_spec.js

ee/spec/frontend/sidebar/mock_data.js