Fix type definitions for milestone resolvers

Add missing type definitions and fix the one for the base class

.rubocop_manual_todo.yml

@@ -51,13 +51,11 @@ Graphql/ResolverType:
     - '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/group_milestones_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_milestones_resolver.rb'
     - 'app/graphql/resolvers/project_pipelines_resolver.rb'
     - 'app/graphql/resolvers/projects/snippets_resolver.rb'
     - 'app/graphql/resolvers/snippets_resolver.rb'

app/graphql/resolvers/group_milestones_resolver.rb

@@ -6,6 +6,8 @@ module Resolvers
              required: false,
              description: 'Also return milestones in all subgroups and subprojects'
 
+    type Types::MilestoneType.connection_type, null: true
+
     private
 
     def parent_id_parameters(args)

app/graphql/resolvers/milestones_resolver.rb

@@ -25,7 +25,7 @@ module Resolvers
              required: false,
              description: 'A date that the milestone contains'
 
-    type Types::MilestoneType, null: true
+    type Types::MilestoneType.connection_type, null: true
 
     def resolve(**args)
       validate_timeframe_params!(args)

app/graphql/resolvers/project_milestones_resolver.rb

@@ -6,6 +6,8 @@ module Resolvers
              required: false,
              description: "Also return milestones in the project's parent group and its ancestors"
 
+    type Types::MilestoneType.connection_type, null: true
+
     private
 
     def parent_id_parameters(args)