Cop multiple field definitions

[toneymathews]

Closes #90
This PR

• adds a cop to group multiple field definitions (MFD) together. If this case, ungrouped definitions will be added following the first field definition
• updates FieldDefinition cop. If there are MFD, the resolver method is added after the last field definition.
  • For MFD, the field node can be same. At the same time, the definitions can be different due to different arguments as in the example below

  field :image_url, String, null: false do
    argument :width, Int, null: true
  end

   field :image_url, String, null: false do
    argument :width, Int, null: true
    argument :height, Int, null: true
  end

So, RuboCop::GraphQL::Field.new now takes in the parent node if field def has a body. Associated changes are made.

There is one odd scenario as described in the example below

class UserType < BaseType
  field :first_name, String, null: true

  def first_name
     object.first_name
  end

  field :last_name, String, null: true

  field :first_name, String, null: false
  field :first_name, Name, null: false 
end

Running GraphQL/FieldDefinitions would add the first_name resolver method after the last field definition.

class UserType < BaseType
  field :first_name, String, null: true

  field :last_name, String, null: true

  field :first_name, String, null: false
  field :first_name, Name, null: false 
  
  def first_name
     object.first_name
  end
end

Then running MFD would lead to

class UserType < BaseType
  field :first_name, String, null: true
  field :first_name, String, null: false
  field :first_name, Name, null: false 

  field :last_name, String, null: true
  
  def first_name
     object.first_name
  end
end

So it's preferable to run GraphQL/MultipleFieldDefinitions before GraphQL/FieldDefinitions. I did not think too much of it since running rubocop a second time would fix this.

[DmitryTsepelev]

LGTM, thank you so much!