feat: Migrate to Google Merchant API and remove Composer dependencies

- Fix ISE 500 error on plugin activation:
  - Defer wc_get_logger() call in Logger class (lazy initialization)
  - Move plugin init to plugins_loaded hook with priority 20
  - Remove invalid Google_Service_ShoppingContent_Reports instantiation

- Migrate from deprecated Content API to new Merchant API:
  - Rewrite Google API class with direct REST calls
  - Implement JWT authentication using PHP OpenSSL
  - Use WordPress wp_remote_* functions for HTTP requests
  - Support Price Competitiveness reports for competitor pricing

- Remove all Composer dependencies:
  - Delete vendor/ directory (~50 packages)
  - Delete composer.json and composer.lock
  - Remove setup scripts and related documentation

- Plugin is now fully self-contained with no external dependencies

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -4,12 +4,13 @@ A production-ready WooCommerce plugin that automatically adjusts sale prices bas
 
 ## Description
 
-This plugin connects to Google Merchant Center API to retrieve competitive pricing data and automatically updates your WooCommerce product prices to stay competitive while maintaining your desired profit margins.
+This plugin connects to the Google Merchant API to retrieve competitive pricing data and automatically updates your WooCommerce product prices to stay competitive while maintaining your desired profit margins.
 
 ## Features
 
 - **Automated Daily Price Updates**: Schedule automatic price adjustments using WordPress cron
-- **Google Merchant Center Integration**: Connects via Google Content API for Shopping
+- **Google Merchant API Integration**: Uses the new Google Merchant API (replaces deprecated Content API)
+- **No External Dependencies**: Self-contained plugin with no Composer requirements
 - **Tax-Aware Pricing**: Handles both tax-inclusive and tax-exclusive pricing configurations
 - **Minimum Margin Protection**: Never sell below your cost + minimum margin
 - **In-Stock Only Processing**: Only updates products that are currently in stock
@@ -22,35 +23,25 @@ This plugin connects to Google Merchant Center API to retrieve competitive prici
 - WordPress 5.8 or higher
 - WooCommerce 5.0 or higher
 - PHP 7.4 or higher
+- PHP OpenSSL extension (for JWT authentication)
 - Google Merchant Center account
-- Google Service Account with Content API access
+- Google Service Account with Merchant API access
 
 ## Installation
 
-### Quick Install (Recommended)
-
-1. Download the plugin with vendor libraries included (complete package)
+1. Download the plugin
 2. Upload to `/wp-content/plugins/informatiq-smart-google-pricing/`
 3. Activate the plugin through the 'Plugins' menu in WordPress
 4. Configure settings under WooCommerce > Smart Pricing
 
-### Manual Setup (If vendor directory is missing)
-
-1. Upload the plugin files to `/wp-content/plugins/informatiq-smart-google-pricing/`
-2. Set up Google API Client library (see `VENDOR-SETUP.md` for details):
-   - **Option A**: Run `composer install` in the plugin directory
-   - **Option B**: Manually download and extract Google API Client to `vendor/` directory
-3. Activate the plugin through the 'Plugins' menu in WordPress
-4. Configure settings under WooCommerce > Smart Pricing
-
-The plugin includes a custom autoloader that works with manually included libraries, so Composer is not required for end users.
+No Composer or external dependencies required - the plugin is fully self-contained.
 
 ## Configuration
 
 ### Google Merchant Center Setup
 
 1. Create a Google Cloud Project
-2. Enable the Content API for Shopping
+2. Enable the Merchant API
 3. Create a Service Account and download the JSON key
 4. Grant the service account access to your Merchant Center account
 
@@ -67,7 +58,7 @@ The plugin includes a custom autoloader that works with manually included librar
 
 1. **Daily Automation**: The plugin runs automatically based on your configured schedule
 2. **Product Matching**: Matches WooCommerce products with Google Merchant Center via SKU/GTIN
-3. **Competitive Analysis**: Retrieves the lowest competitor price from Google
+3. **Competitive Analysis**: Retrieves competitive pricing data from Google's Price Competitiveness reports
 4. **Price Calculation**:
    - Calculates new price as: Competitor Price - Random Offset (0.05-0.20)
    - Ensures price never goes below Cost + Minimum Margin
@@ -123,9 +114,7 @@ The plugin supports multiple update frequencies:
 - Twice daily (every 12 hours)
 - Every 6 hours
 
-## Development
-
-### File Structure
+## File Structure
 
 ```
 informatiq-smart-google-pricing/
@@ -141,22 +130,19 @@ informatiq-smart-google-pricing/
 │   ├── class-informatiq-sp-logger.php
 │   ├── class-informatiq-sp-price-updater.php
 │   └── class-informatiq-sp-scheduler.php
-├── composer.json
+├── languages/
 ├── informatiq-smart-google-pricing.php
 ├── README.md
 └── uninstall.php
 ```
 
-### Dependencies
+## API Notes
 
-The plugin uses Composer for dependency management:
+This plugin uses the new Google Merchant API which replaces the deprecated Content API for Shopping. Key differences:
 
-```bash
-composer install
-```
-
-Main dependencies:
-- `google/apiclient`: ^2.15
+- **Base URL**: `https://merchantapi.googleapis.com`
+- **Pricing**: Amounts are in micros (1,000,000 micros = 1 unit of currency)
+- **Resource naming**: Uses hierarchical names like `accounts/{id}/products/{product}`
 
 ## Support
 
@@ -174,6 +160,12 @@ GPL v2 or later
 
 ## Changelog
 
+### 2.0.0
+- Migrated to Google Merchant API (from deprecated Content API)
+- Removed Composer/vendor dependencies
+- Self-contained plugin with direct REST API calls
+- JWT-based authentication using PHP OpenSSL
+
 ### 1.0.0
 - Initial release
 - Google Merchant Center integration