DEVDOCS-6090: [Update] Add channels (#481)

<!-- Ticket number or summary of work -->
# [DEVDOCS-6090]


## What changed?
Added channels as an optional field to existing /catalog/products v3
endpoints

## Release notes draft

* We're happy to announce channels are available as an optional field in
/catalog/products v3 endpoints which can help you .......

## Anything else?
<!-- Add related PRs, salient notes, additional ticket numbers, etc. -->

ping {names}


[DEVDOCS-6090]:
https://bigcommercecloud.atlassian.net/browse/DEVDOCS-6090?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

reference/catalog/products_catalog.v3.yml

@@ -176,6 +176,8 @@ paths:
                 product_tax_code: string
                 categories:
                   - 0
+                channels:
+                  - 1
                 brand_id: 37
                 inventory_level: 0
                 inventory_warning_level: 0
@@ -6594,6 +6596,8 @@ components:
             product_tax_code: string
             categories:
               - 0
+            channels:
+              - 1
             brand_id: 0
             brand_name: "New Brand"
             inventory_level: 0
@@ -6872,6 +6876,8 @@ components:
               calculated_price: 50
               categories:
                 - 24
+              channels:
+                - 1
               brand_id: 37
               brand_name: "New Brand"
               option_set_id: 21
@@ -7037,6 +7043,12 @@ components:
             type: number
           maximum: 1000
           minimum: 0
+        channels:
+          type: array
+          description: | 
+            An array of channel IDs to which this product is assigned.
+          items:
+            type: number
         brand_id:
           maximum: 1000000000
           minimum: 0
@@ -7374,6 +7386,8 @@ components:
               calculated_price: 50
               categories:
                 - 24
+              channels:
+                - 1
               brand_id: 37
               option_set_id: 21
               option_set_display: "right"
@@ -7534,6 +7548,12 @@ components:
             type: number
           maximum: 1000
           minimum: 0
+        channels:
+          type: array
+          description: | 
+            An array of channel IDs to which this product is assigned.
+          items:
+            type: number
         brand_id:
           maximum: 1000000000
           minimum: 0
@@ -9104,6 +9124,7 @@ components:
             - options
             - parent_relations
             - custom_fields
+            - channels
     IdMinParam:
       name: 'id:min'
       in: query