misc: Cleanup remaining group logic (getlago#2310)

## Context

Related to getlago#2257

## Description

This PR removes some remaining legacy group related logic

app/queries/past_usage_query.rb

@@ -39,7 +39,7 @@ def query
   end
 
   def fees_query(invoice)
-    query = invoice.fees.charge.includes(:charge_filter, :group)
+    query = invoice.fees.charge.includes(:charge_filter)
     return query unless filters.billable_metric_code
 
     query.joins(:charge).where(charges: {billable_metric_id: billable_metric.id})

app/serializers/v1/invoice_serializer.rb

@@ -60,7 +60,6 @@ def fees
             :subscription,
             :customer,
             :charge,
-            :group,
             :billable_metric,
             {charge_filter: {values: :billable_metric_filter}}
           ]

app/services/charges/override_service.rb

@@ -17,7 +17,6 @@ def call
           c.properties = params[:properties] if params.key?(:properties)
           c.min_amount_cents = params[:min_amount_cents] if params.key?(:min_amount_cents)
           c.invoice_display_name = params[:invoice_display_name] if params.key?(:invoice_display_name)
-          c.group_properties = charge.group_properties.map(&:dup)
           c.filters = charge.filters.map do |filter|
             f = filter.dup
             f.values = filter.values.map(&:dup)
@@ -27,14 +26,6 @@ def call
         end
         new_charge.save!
 
-        if params.key?(:group_properties)
-          group_result = GroupProperties::CreateOrUpdateBatchService.call(
-            charge: new_charge,
-            properties_params: params[:group_properties]
-          )
-          group_result.raise_if_error!
-        end
-
         if params.key?(:filters)
           filters_result = ChargeFilters::CreateOrUpdateBatchService.call(
             charge: new_charge,

app/services/events/stores/base_store.rb

@@ -8,7 +8,6 @@ def initialize(code:, subscription:, boundaries:, filters: {})
         @subscription = subscription
         @boundaries = boundaries
 
-        @group = filters[:group]
         @grouped_by = filters[:grouped_by]
         @grouped_by_values = filters[:grouped_by_values]
 
@@ -114,7 +113,7 @@ def sanitize_colon(query)
 
       protected
 
-      attr_accessor :code, :subscription, :group, :boundaries, :grouped_by_values, :matching_filters, :ignored_filters
+      attr_accessor :code, :subscription, :boundaries, :grouped_by_values, :matching_filters, :ignored_filters
 
       delegate :customer, to: :subscription