feat(tresholds): Add GraphQL for usage thresholds (#2397)

## Roadmap Task

👉  https://getlago.canny.io/feature-requests/p/progressive-billing

## Context

There's always a risk of customers not paying invoices generated at the
end of a billing period. It would be beneficial to bill customers at
given thresholds (units vs. amount) rather than waiting until the end of
the period. This approach would allow for removing customer access if
invoices are not paid and prevent having a highest amount of unpaid
invoices.

## Description

Add GraphQL for usage thresholds.

app/graphql/mutations/plans/create.rb

@@ -25,6 +25,7 @@ class Create < BaseMutation
 
       argument :charges, [Types::Charges::Input]
       argument :minimum_commitment, Types::Commitments::Input, required: false
+      argument :usage_thresholds, [Types::UsageThresholds::Input], required: false
 
       type Types::Plans::Object
 

app/graphql/mutations/plans/update.rb

@@ -25,6 +25,7 @@ class Update < BaseMutation
 
       argument :charges, [Types::Charges::Input]
       argument :minimum_commitment, Types::Commitments::Input, required: false
+      argument :usage_thresholds, [Types::UsageThresholds::Input], required: false
 
       type Types::Plans::Object
 

app/graphql/types/plans/object.rb

@@ -20,6 +20,7 @@ class Object < Types::BaseObject
       field :parent, Types::Plans::Object, null: true
       field :pay_in_advance, Boolean, null: false
       field :trial_period, Float
+      field :usage_thresholds, [Types::UsageThresholds::Object]
 
       field :charges, [Types::Charges::Object]
       field :taxes, [Types::Taxes::Object]

app/graphql/types/subscriptions/plan_overrides_input.rb

@@ -12,6 +12,7 @@ class PlanOverridesInput < Types::BaseInputObject
       argument :name, String, required: false
       argument :tax_codes, [String], required: false
       argument :trial_period, Float, required: false
+      argument :usage_thresholds, [Types::Subscriptions::UsageThresholdOverridesInput], required: false
     end
   end
 end

app/graphql/types/subscriptions/usage_threshold_overrides_input.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Types
+  module Subscriptions
+    class UsageThresholdOverridesInput < Types::BaseInputObject
+      argument :amount_cents, GraphQL::Types::BigInt, required: true
+      argument :recurring, Boolean, required: false
+      argument :threshold_display_name, String, required: false
+    end
+  end
+end

app/graphql/types/usage_thresholds/input.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+module Types
+  module UsageThresholds
+    class Input < BaseInputObject
+      graphql_name 'UsageThresholdInput'
+
+      argument :id, ID, required: false
+
+      argument :amount_cents, GraphQL::Types::BigInt, required: false
+      argument :recurring, Boolean, required: false
+      argument :threshold_display_name, String, required: false
+    end
+  end
+end

app/graphql/types/usage_thresholds/object.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module Types
+  module UsageThresholds
+    class Object < Types::BaseObject
+      graphql_name 'UsageThreshold'
+
+      field :id, ID, null: false
+
+      field :amount_cents, GraphQL::Types::BigInt, null: false
+      field :recurring, Boolean, null: false
+      field :threshold_display_name, String, null: true
+
+      field :created_at, GraphQL::Types::ISO8601DateTime, null: false
+      field :updated_at, GraphQL::Types::ISO8601DateTime, null: false
+    end
+  end
+end

app/services/plans/override_service.rb

@@ -36,14 +36,11 @@ def call
           Charges::OverrideService.call(charge:, params: charge_params)
         end
 
-        if License.premium? && plan.organization.premium_integrations.include?('progressive_billing')
-          plan.usage_thresholds.find_each do |threshold|
-            threshold_params = (
-              params[:usage_thresholds]&.find { |p| p[:id] == threshold.id } || {}
-            ).merge(plan_id: new_plan.id)
-
-            UsageThresholds::OverrideService.call(threshold:, params: threshold_params)
-          end
+        if params[:usage_thresholds].present? &&
+            License.premium? &&
+            plan.organization.premium_integrations.include?('progressive_billing')
+
+          UsageThresholds::OverrideService.call(usage_thresholds_params: params[:usage_thresholds], new_plan: new_plan)
         end
 
         if params[:minimum_commitment].present? && License.premium?

app/services/usage_thresholds/override_service.rb

@@ -2,35 +2,36 @@
 
 module UsageThresholds
   class OverrideService < BaseService
-    def initialize(threshold:, params:)
-      @threshold = threshold
-      @params = params
+    def initialize(usage_thresholds_params:, new_plan:)
+      @usage_thresholds_params = usage_thresholds_params
+      @new_plan = new_plan
 
       super
     end
 
     def call
       ActiveRecord::Base.transaction do
-        new_threshold = threshold.dup.tap do |c|
-          c.amount_cents = params[:amount_cents] if params.key?(:amount_cents)
-          c.recurring = params[:recurring] if params.key?(:recurring)
-          c.threshold_display_name = params[:threshold_display_name] if params.key?(:threshold_display_name)
-          c.plan_id = params[:plan_id]
-        end
-        new_threshold.save!
+        usage_thresholds_params.each do |params|
+          usage_threshold = new_plan.usage_thresholds.new(
+            plan_id: new_plan.id,
+            threshold_display_name: params[:threshold_display_name],
+            amount_cents: params[:amount_cents],
+            recurring: params[:recurring] || false
+          )
 
-        result.usage_threshold = new_threshold
+          usage_threshold.save!
+        end
       end
 
+      result.usage_thresholds = new_plan.usage_thresholds
       result
     rescue ActiveRecord::RecordInvalid => e
       result.record_validation_failure!(record: e.record)
-    rescue BaseService::FailedResult => e
-      e.result
+      result.fail_with_error!
     end
 
     private
 
-    attr_reader :threshold, :params
+    attr_reader :usage_thresholds_params, :new_plan
   end
 end