chore: make apis nullable (#7763)

what:

- makes top level attributes of each object an optional field in the http layer where possible

RESOLVES CORE-2229

packages/modules/pricing/src/types/services/price-list.ts

@@ -13,6 +13,7 @@ export interface CreatePriceListDTO {
 export interface UpdatePriceListDTO {
   id: string
   title?: string
+  description?: string | null
   starts_at?: string | null
   ends_at?: string | null
   status?: PriceListStatus

packages/modules/promotion/src/types/campaign.ts

@@ -3,19 +3,19 @@ import { Promotion } from "@models"
 
 export interface CreateCampaignDTO {
   name: string
-  description?: string
+  description?: string | null
   campaign_identifier: string
-  starts_at?: Date
-  ends_at?: Date
+  starts_at?: Date | null
+  ends_at?: Date | null
   promotions?: (PromotionDTO | Promotion)[]
 }
 
 export interface UpdateCampaignDTO {
   id: string
   name?: string
-  description?: string
+  description?: string | null
   campaign_identifier?: string
-  starts_at?: Date
-  ends_at?: Date
+  starts_at?: Date | null
+  ends_at?: Date | null
   promotions?: (PromotionDTO | Promotion)[]
 }