Add type annotations to graphql resolvers

This adds some missing type annotations, and correct some incorrect
ones. Where possible, we remove duplication by using resolvers to
provide field options.

.rubocop_manual_todo.yml

@@ -47,13 +47,8 @@ Graphql/ResolverType:
     - 'app/graphql/resolvers/ci/pipeline_stages_resolver.rb'
     - 'app/graphql/resolvers/commit_pipelines_resolver.rb'
     - 'app/graphql/resolvers/error_tracking/sentry_error_stack_trace_resolver.rb'
-    - 'app/graphql/resolvers/group_issues_resolver.rb'
-    - 'app/graphql/resolvers/group_merge_requests_resolver.rb'
-    - 'app/graphql/resolvers/members_resolver.rb'
     - 'app/graphql/resolvers/merge_request_pipelines_resolver.rb'
-    - 'app/graphql/resolvers/merge_request_resolver.rb'
     - 'app/graphql/resolvers/merge_requests_resolver.rb'
-    - 'app/graphql/resolvers/project_merge_requests_resolver.rb'
     - 'app/graphql/resolvers/project_pipelines_resolver.rb'
     - 'app/graphql/resolvers/users/group_count_resolver.rb'
     - 'ee/app/graphql/resolvers/ci/jobs_resolver.rb'

app/graphql/resolvers/concerns/looks_ahead.rb

@@ -4,6 +4,7 @@ module LooksAhead
   extend ActiveSupport::Concern
 
   included do
+    extras [:lookahead]
     attr_accessor :lookahead
   end
 

app/graphql/resolvers/group_issues_resolver.rb

 # frozen_string_literal: true
+# rubocop:disable Graphql/ResolverType (inherited from IssuesResolver)
 
 module Resolvers
   class GroupIssuesResolver < IssuesResolver

app/graphql/resolvers/group_merge_requests_resolver.rb

@@ -6,6 +6,8 @@ module Resolvers
 
     alias_method :group, :synchronized_object
 
+    type Types::MergeRequestType.connection_type, null: true
+
     include_subgroups 'merge requests'
     accept_assignee
     accept_author

app/graphql/resolvers/group_milestones_resolver.rb

 # frozen_string_literal: true
+# rubocop:disable Graphql/ResolverType (inherited from MilestonesResolver)
 
 module Resolvers
   class GroupMilestonesResolver < MilestonesResolver

app/graphql/resolvers/members_resolver.rb

@@ -5,6 +5,8 @@ module Resolvers
     include Gitlab::Graphql::Authorize::AuthorizeResource
     include LooksAhead
 
+    type Types::MemberInterface.connection_type, null: true
+
     argument :search, GraphQL::STRING_TYPE,
               required: false,
               description: 'Search query'

app/graphql/resolvers/merge_request_resolver.rb

@@ -6,6 +6,8 @@ module Resolvers
 
     alias_method :project, :synchronized_object
 
+    type ::Types::MergeRequestType, null: true
+
     argument :iid, GraphQL::STRING_TYPE,
               required: true,
               as: :iids,

app/graphql/resolvers/project_members_resolver.rb

 # frozen_string_literal: true
+# rubocop:disable Graphql/ResolverType (inherited from MembersResolver)
 
 module Resolvers
   class ProjectMembersResolver < MembersResolver
-    type Types::MemberInterface, null: true
-
     authorize :read_project_member
 
     private

app/graphql/resolvers/project_merge_requests_resolver.rb

@@ -2,6 +2,7 @@
 
 module Resolvers
   class ProjectMergeRequestsResolver < MergeRequestsResolver
+    type ::Types::MergeRequestType.connection_type, null: true
     accept_assignee
     accept_author
   end

app/graphql/resolvers/project_milestones_resolver.rb

 # frozen_string_literal: true
+# rubocop:disable Graphql/ResolverType (inherited from MilestonesResolver)
 
 module Resolvers
   class ProjectMilestonesResolver < MilestonesResolver

app/graphql/resolvers/projects/snippets_resolver.rb

 # frozen_string_literal: true
-# rubocop:disable Graphql/ResolverType
+# rubocop:disable Graphql/ResolverType (inherited from ResolvesSnippets)
 
 module Resolvers
   module Projects

app/graphql/resolvers/snippets_resolver.rb

 # frozen_string_literal: true
-# rubocop:disable Graphql/ResolverType
+# rubocop:disable Graphql/ResolverType (inherited from ResolvesSnippets)
 
 module Resolvers
   class SnippetsResolver < BaseResolver

app/graphql/resolvers/users/snippets_resolver.rb

 # frozen_string_literal: true
-# rubocop:disable Graphql/ResolverType
+# rubocop:disable Graphql/ResolverType (inherited from ResolvesSnippets)
 
 module Resolvers
   module Users

app/graphql/types/group_type.rb

@@ -82,9 +82,7 @@ module Types
           end
 
     field :group_members,
-          Types::GroupMemberType.connection_type,
           description: 'A membership of a user within this group',
-          extras: [:lookahead],
           resolver: Resolvers::GroupMembersResolver
 
     field :container_repositories,

app/graphql/types/project_type.rb

@@ -161,7 +161,6 @@ module Types
           resolver: Resolvers::ProjectMilestonesResolver
 
     field :project_members,
-          Types::MemberInterface.connection_type,
           description: 'Members of the project',
           resolver: Resolvers::ProjectMembersResolver