feat(certificates): add custom provisioning option

readme.hints.md

@@ -295,4 +295,54 @@ You'll see:
 - During attacks or high-volume scenarios, logs are flushed more frequently
 - If 50+ events occur within 1 second, immediate flush is triggered
 - Prevents memory buildup during flooding attacks
-- Maintains real-time visibility during incidents
+- Maintains real-time visibility during incidents
+
+## Custom Certificate Provision Function
+
+The `certProvisionFunction` feature has been implemented to allow users to provide their own certificate generation logic.
+
+### Implementation Details
+
+1. **Type Definition**: The function must return `Promise<TSmartProxyCertProvisionObject>` where:
+   - `TSmartProxyCertProvisionObject = plugins.tsclass.network.ICert | 'http01'`
+   - Return `'http01'` to fallback to Let's Encrypt
+   - Return a certificate object for custom certificates
+
+2. **Certificate Manager Changes**:
+   - Added `certProvisionFunction` property to CertificateManager
+   - Modified `provisionAcmeCertificate()` to check custom function first
+   - Custom certificates are stored with source type 'custom'
+   - Expiry date extraction currently defaults to 90 days
+
+3. **Configuration Options**:
+   - `certProvisionFunction`: The custom provision function
+   - `certProvisionFallbackToAcme`: Whether to fallback to ACME on error (default: true)
+
+4. **Usage Example**:
+```typescript
+new SmartProxy({
+  certProvisionFunction: async (domain: string) => {
+    if (domain === 'internal.example.com') {
+      return {
+        cert: customCert,
+        key: customKey,
+        ca: customCA
+      } as unknown as TSmartProxyCertProvisionObject;
+    }
+    return 'http01'; // Use Let's Encrypt
+  },
+  certProvisionFallbackToAcme: true
+})
+```
+
+5. **Testing Notes**:
+   - Type assertions through `unknown` are needed in tests due to strict interface typing
+   - Mock certificate objects work for testing but need proper type casting
+   - The actual certificate parsing for expiry dates would need a proper X.509 parser
+
+### Future Improvements
+
+1. Implement proper certificate expiry date extraction using X.509 parsing
+2. Add support for returning expiry date with custom certificates
+3. Consider adding validation for custom certificate format
+4. Add events/hooks for certificate provisioning lifecycle