Add webhook notification functionality with configuration options

README.md

@@ -66,7 +66,9 @@ You will need these env variables from the application settings:
 EVE_SSO_CLIENT_ID=Client ID
 EVE_SSO_SECRET=Secret Key
 EVE_SSO_CALLBACK_URL=Callback URL (This should be the domain you are hosting at or if run locally it should be http://localhost:3000)
-WEBHOOK_URL=Discord webhook URL for notifications (optional)
+
+# Webhook Configuration (optional)
+WEBHOOK_URL=Discord webhook URL for notifications
 ```
 
 ## Run locally
@@ -85,11 +87,44 @@ The application supports webhook notifications for various PI events:
 - **Launch pad capacity warnings**: Notify when launch pads are about to be full (configurable percentage)
 - **Launch pad full**: Notify when launch pads are at 100% capacity
 
+### Webhook Configuration
+
 To enable webhook notifications:
 
-1. Set the `WEBHOOK_URL` environment variable to your Discord webhook URL
-2. Enable webhook notifications in the Settings dialog
-3. Configure warning thresholds for extractors, storage, and launch pads
+1. Set the `WEBHOOK_URL` environment variable to your Discord webhook URL or other webhook endpoint
+2. Open the Settings dialog in the application and enable webhook notifications
+3. Configure thresholds in the Settings dialog:
+   - **Extractor Expiry Warning**: How early to warn about extractor expiry (ISO 8601 duration format, default: P12H = 12 hours)
+   - **Storage Warning Threshold**: Storage fill percentage for warnings (default: 85%)
+   - **Storage Critical Threshold**: Storage fill percentage for critical alerts (default: 100%)
+
+### Webhook Behavior
+
+- **Automatic checks**: Runs every minute to check extractor expiry and storage levels
+- **Data fetch checks**: Also checks when planet data is refreshed
+- **Duplicate prevention**: Won't send the same alert repeatedly within cooldown periods
+- **State reset**: Extractor alerts reset when extractors are restarted with fresh cycles
+
+### Webhook Payload Format
+
+The webhook sends JSON payloads with this structure:
+
+```json
+{
+  "type": "extractor_expiring|extractor_expired|storage_almost_full|storage_full|launchpad_almost_full|launchpad_full",
+  "message": "Human readable message",
+  "characterName": "Character Name",
+  "planetName": "Planet Name",
+  "details": {
+    "extractorType": "Product Type",
+    "hoursRemaining": 1.5,
+    "storageUsed": 8500,
+    "storageCapacity": 10000,
+    "fillPercentage": 85.0
+  },
+  "timestamp": "2024-01-01T12:00:00.000Z"
+}
+```
 
 The webhook URL is kept secure in environment variables and not stored in the browser.