Fix rubocop errors by adding type annotations

This types user merge request resolvers as returning Merge Request
connections.

Additionally, the base class is renamed so it is not mistaken for an
actual resolver.

.rubocop_manual_todo.yml

@@ -47,8 +47,6 @@ Graphql/IDType:
 
 Graphql/ResolverType:
   Exclude:
-    - 'app/graphql/resolvers/assigned_merge_requests_resolver.rb'
-    - 'app/graphql/resolvers/authored_merge_requests_resolver.rb'
     - 'app/graphql/resolvers/base_resolver.rb'
     - 'app/graphql/resolvers/ci/pipeline_stages_resolver.rb'
     - 'app/graphql/resolvers/commit_pipelines_resolver.rb'
@@ -65,7 +63,6 @@ Graphql/ResolverType:
     - 'app/graphql/resolvers/project_pipelines_resolver.rb'
     - 'app/graphql/resolvers/projects/snippets_resolver.rb'
     - 'app/graphql/resolvers/snippets_resolver.rb'
-    - 'app/graphql/resolvers/user_merge_requests_resolver.rb'
     - 'app/graphql/resolvers/users/group_count_resolver.rb'
     - 'app/graphql/resolvers/users/snippets_resolver.rb'
     - 'ee/app/graphql/resolvers/ci/jobs_resolver.rb'

app/graphql/resolvers/assigned_merge_requests_resolver.rb

 # frozen_string_literal: true
 
 module Resolvers
-  class AssignedMergeRequestsResolver < UserMergeRequestsResolver
+  class AssignedMergeRequestsResolver < UserMergeRequestsResolverBase
+    type ::Types::MergeRequestType.connection_type, null: true
     accept_author
 
     def user_role

app/graphql/resolvers/authored_merge_requests_resolver.rb

 # frozen_string_literal: true
 
 module Resolvers
-  class AuthoredMergeRequestsResolver < UserMergeRequestsResolver
+  class AuthoredMergeRequestsResolver < UserMergeRequestsResolverBase
+    type ::Types::MergeRequestType.connection_type, null: true
     accept_assignee
 
     def user_role

app/graphql/resolvers/user_merge_requests_resolver.rb → app/graphql/resolvers/user_merge_requests_resolver_base.rb

 # frozen_string_literal: true
 
 module Resolvers
-  class UserMergeRequestsResolver < MergeRequestsResolver
+  class UserMergeRequestsResolverBase < MergeRequestsResolver
     include ResolvesProject
 
     argument :project_path, GraphQL::STRING_TYPE,

app/graphql/types/user_type.rb

@@ -46,10 +46,10 @@ module Types
           resolver: Resolvers::UserStarredProjectsResolver
 
     # Merge request field: MRs can be either authored or assigned:
-    field :authored_merge_requests, Types::MergeRequestType.connection_type, null: true,
+    field :authored_merge_requests,
           resolver: Resolvers::AuthoredMergeRequestsResolver,
           description: 'Merge Requests authored by the user'
-    field :assigned_merge_requests, Types::MergeRequestType.connection_type, null: true,
+    field :assigned_merge_requests,
           resolver: Resolvers::AssignedMergeRequestsResolver,
           description: 'Merge Requests assigned to the user'