Add correct types and descriptions

This fixes some errors and omissions in our schema.

- Correct type nullability for snippets resolvers
- Specify correct type for user starred projects resolver
- Add description to User type

Fixes a test failure due to change of resolver type (the resolver
now, correctly, returns a connection, which needs different handling).

app/graphql/resolvers/ci/runner_platforms_resolver.rb

@@ -3,7 +3,8 @@
 module Resolvers
   module Ci
     class RunnerPlatformsResolver < BaseResolver
-      type Types::Ci::RunnerPlatformType, null: false
+      type Types::Ci::RunnerPlatformType.connection_type, null: true
+      description 'Supported runner platforms.'
 
       def resolve(**args)
         runner_instructions.map do |platform, data|

app/graphql/resolvers/ci/runner_setup_resolver.rb

@@ -4,6 +4,7 @@ module Resolvers
   module Ci
     class RunnerSetupResolver < BaseResolver
       type Types::Ci::RunnerSetupType, null: true
+      description 'Runner setup instructions.'
 
       argument :platform, GraphQL::STRING_TYPE,
         required: true,

app/graphql/resolvers/concerns/resolves_snippets.rb

@@ -4,7 +4,7 @@ module ResolvesSnippets
   extend ActiveSupport::Concern
 
   included do
-    type Types::SnippetType.connection_type, null: false
+    type Types::SnippetType.connection_type, null: true
 
     argument :ids, [::Types::GlobalIDType[::Snippet]],
              required: false,

app/graphql/resolvers/user_starred_projects_resolver.rb

@@ -2,7 +2,7 @@
 
 module Resolvers
   class UserStarredProjectsResolver < BaseResolver
-    type Types::ProjectType, null: true
+    type Types::ProjectType.connection_type, null: true
 
     argument :search, GraphQL::STRING_TYPE,
               required: false,

app/graphql/types/user_type.rb

@@ -3,6 +3,7 @@
 module Types
   class UserType < BaseObject
     graphql_name 'User'
+    description 'Representation of a GitLab user.'
 
     authorize :read_user
 

spec/graphql/resolvers/ci/runner_platforms_resolver_spec.rb

@@ -9,7 +9,7 @@ RSpec.describe Resolvers::Ci::RunnerPlatformsResolver do
     subject(:resolve_subject) { resolve(described_class) }
 
     it 'returns all possible runner platforms' do
-      expect(resolve_subject).to include(
+      expect(resolve_subject).to contain_exactly(
         hash_including(name: :linux), hash_including(name: :osx),
         hash_including(name: :windows), hash_including(name: :docker),
         hash_including(name: :kubernetes)