graphql-ruby: fix create_link_test

[jcat4]

On part 3 of the graphql-ruby tutorial, the code for the Mutations::CreateLinkTest class doesn't run.

Error:
Mutations::CreateLinkTest#test_create_a_new_link:
ArgumentError: wrong number of arguments (given 1, expected 0)
    app/graphql/mutations/create_link.rb:10:in `resolve'
    test/graphql/mutations/create_link_test.rb:6:in `perform'
    test/graphql/mutations/create_link_test.rb:10:in `block in <class:CreateLinkTest>'

This is because the test's perform method takes a keyword argument args, but doesn't splat it before sending it to Mutations::CreateLink#resolve. Because of this, Mutations::CreateLink#resolve is receiving a single hash argument when it expects 2 keyword arguments.

# Mutations::CreateLinkTest
def perform(user: nil, **args)
  Mutations::CreateLink.new(object: nil, field: nil, context: {}).resolve(args)
end
  
# Mutations::CreateLink
def resolve(description: nil, url: nil)
  Link.create!(description: description, url: url)
end

Splatting args fixes the problem!

# Mutations::CreateLinkTest
def perform(user: nil, **args)
  Mutations::CreateLink.new(object: nil, field: nil, context: {}).resolve(**args)
end

[TasinIshmam]

Thank you! Merged.