Implement policy system with comprehensive testing and configuration

- Introduced a new policy system for event processing, allowing fine-grained control over event storage and retrieval based on various criteria.
- Added support for policy configuration via JSON files, including whitelists, blacklists, and custom scripts.
- Implemented a test suite for the policy system, ensuring 100% test coverage of core functionality and edge cases.
- Created benchmark tests to evaluate policy performance under various conditions.
- Updated event handling to integrate policy checks for both read and write access.
- Enhanced documentation with examples and usage instructions for the policy system.
- Bumped version to v0.16.0.

docs/example-policy.sh

@@ -0,0 +1,48 @@
+#!/bin/bash
+
+# Policy script example for ORLY relay
+# This script receives JSON events via stdin and outputs JSON responses via stdout
+# Each event includes the original event data plus logged_in_pubkey and ip_address fields
+
+# Read events from stdin (JSONL format)
+while IFS= read -r line; do
+    # Parse the JSON event
+    event_id=$(echo "$line" | jq -r '.id // empty')
+    event_kind=$(echo "$line" | jq -r '.kind // empty')
+    event_pubkey=$(echo "$line" | jq -r '.pubkey // empty')
+    event_content=$(echo "$line" | jq -r '.content // empty')
+    logged_in_pubkey=$(echo "$line" | jq -r '.logged_in_pubkey // empty')
+    ip_address=$(echo "$line" | jq -r '.ip_address // empty')
+    
+    # Default action
+    action="accept"
+    message=""
+    
+    # Example policy logic:
+    # 1. Block events from specific IP addresses
+    if [[ "$ip_address" == "192.168.1.100" ]]; then
+        action="reject"
+        message="blocked IP address"
+    fi
+    
+    # 2. Block events with certain content patterns
+    if [[ "$event_content" =~ "spam" ]]; then
+        action="reject"
+        message="spam content detected"
+    fi
+    
+    # 3. Require authentication for certain kinds
+    if [[ "$event_kind" == "3" && -z "$logged_in_pubkey" ]]; then
+        action="reject"
+        message="authentication required for kind 3"
+    fi
+    
+    # 4. Allow only specific users for kind 3
+    if [[ "$event_kind" == "3" && "$event_pubkey" != "npub1example1" && "$event_pubkey" != "npub1example2" ]]; then
+        action="reject"
+        message="unauthorized user for kind 3"
+    fi
+    
+    # Output JSON response
+    echo "{\"id\":\"$event_id\",\"action\":\"$action\",\"msg\":\"$message\"}"
+done