Parse invoice XML files and update sales opportunities in GoHighLevel

Description

Quick overview
This workflow receives a posted invoice XML file via webhook, parses it into JSON, and for each invoice searches and updates a matching GoHighLevel (LeadConnector) opportunity with invoiced amount, pipeline stage, and custom field values.

How it works
Receives a POST request to an n8n webhook containing a binary invoice XML file.
Extracts and decodes the XML content from the uploaded binary file.
Converts the raw XML string into a structured JSON object.
Iterates through each invoice record in the parsed payload.
Calls the GoHighLevel (LeadConnector) Opportunities Search API to find an opportunity by order reference (configured as a test query).
Updates the matched GoHighLevel opportunity with monetary value, pipeline and stage IDs, and custom fields such as invoiced amount and transaction date.

Setup
Configure the source system (warehouse ERP or middleware) to POST the invoice XML file to the webhook URL for the invoice-webhook path.
Add your GoHighLevel (LeadConnector) Private Integration token and replace YOUR_GHL_API_TOKEN in both HTTP requests.
Replace YOUR_GHL_LOCATION_ID, YOUR_GHL_PIPELINE_ID, YOUR_GHL_PIPELINE_STAGE_ID, and the three custom field IDs in the update request body.
Update the opportunity search payload to use the real order reference from the parsed invoice instead of the placeholder YOUR_TEST_ORDER_REF.
Send a sample XML invoice to the webhook to verify parsing and updates, then activate the workflow.