curl --request GET \
  --url https://api.hubapi.com/conversations/v3/custom-channels/

{
  "total": 123,
  "paging": {
    "next": {
      "link": "",
      "after": ""
    }
  },
  "results": [
    {
      "channelDescription": "<string>",
      "createdAt": "2023-11-07T05:31:56Z",
      "capabilities": "{\"richText\":[\"HYPERLINK\",\"TEXT_ALIGNMENT\",\"BLOCKQUOTE\"],\"threadingModel\":\"DELIVERY_IDENTIFIER | INTEGRATION_THREAD_ID\",\"allowInlineImages\":false,\"allowOutgoingMessages\":false,\"allowConversationStart\":false,\"maxFileAttachmentCount\":1,\"allowMultipleRecipients\":false,\"deliveryIdentifierTypes\":[],\"outgoingAttachmentTypes\":[\"FILE\"],\"maxFileAttachmentSizeBytes\":1500000,\"allowedFileAttachmentMimeTypes\":[\"image/png\"],\"maxTotalFileAttachmentSizeBytes\":1500000}",
      "channelAccountConnectionRedirectUrl": "<string>",
      "channelLogoUrl": "<string>",
      "name": "<string>",
      "id": "<string>",
      "webhookUrl": "<string>"
    }
  ]
}