Add IP Whitelist Plugin and corresponding tests

- Introduced `IpWhitelistPlugin` (DOMAIN): Restricts access to specific IP addresses or CIDR ranges.
- Added configuration options: `enabled`, `allowed_ips`, and `status_code`.
- Updated `plugins.md` and `plugin-development.md` to document `IpWhitelistPlugin`.
- Created fixtures for `services-with-ip-whitelist`.
- Added extensive test cases for `IpWhitelistPlugin` to validate configuration and HAProxy output generation.
- Ensured seamless integration into the plugin framework alongside other domain plugins.

src/plugins/builtin/ip_whitelist.py

@@ -0,0 +1,107 @@
+"""
+IP Whitelist Plugin for EasyHAProxy
+
+This plugin restricts access to a domain to only specific IP addresses or CIDR ranges.
+It runs as a DOMAIN plugin (once per domain).
+
+Configuration:
+    - enabled: Enable/disable the plugin (default: true)
+    - allowed_ips: Comma-separated list of IPs/CIDR ranges to allow
+    - status_code: HTTP status code to return for blocked IPs (default: 403)
+
+Example YAML config:
+    plugins:
+      ip_whitelist:
+        enabled: true
+        allowed_ips: "192.168.1.0/24,10.0.0.1,172.16.0.0/16"
+        status_code: 403
+
+Example Container Label:
+    easyhaproxy.http.plugins: "ip_whitelist"
+    easyhaproxy.http.plugin.ip_whitelist.allowed_ips: "192.168.1.0/24,10.0.0.1"
+    easyhaproxy.http.plugin.ip_whitelist.status_code: 403
+
+HAProxy Config Generated:
+    # IP Whitelist - Only allow specific IPs
+    acl whitelisted_ip src 192.168.1.0/24 10.0.0.1
+    http-request deny deny_status 403 if !whitelisted_ip
+"""
+
+import os
+import sys
+
+# Add parent directory to path for imports
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+from plugins import PluginInterface, PluginType, PluginContext, PluginResult
+
+
+class IpWhitelistPlugin(PluginInterface):
+    """Plugin to restrict access to specific IP addresses"""
+
+    def __init__(self):
+        self.enabled = True
+        self.allowed_ips = []
+        self.status_code = 403
+
+    @property
+    def name(self) -> str:
+        return "ip_whitelist"
+
+    @property
+    def plugin_type(self) -> PluginType:
+        return PluginType.DOMAIN
+
+    def configure(self, config: dict) -> None:
+        """
+        Configure the plugin
+
+        Args:
+            config: Dictionary with configuration options
+                - enabled: Whether plugin is enabled
+                - allowed_ips: Comma-separated list of IPs/CIDR ranges
+                - status_code: HTTP status code to return for denied requests
+        """
+        if "enabled" in config:
+            self.enabled = str(config["enabled"]).lower() in ["true", "1", "yes"]
+
+        if "allowed_ips" in config:
+            ips_str = str(config["allowed_ips"])
+            self.allowed_ips = [ip.strip() for ip in ips_str.split(",") if ip.strip()]
+
+        if "status_code" in config:
+            try:
+                self.status_code = int(config["status_code"])
+            except ValueError:
+                self.status_code = 403
+
+    def process(self, context: PluginContext) -> PluginResult:
+        """
+        Generate HAProxy config to whitelist specific IPs
+
+        Args:
+            context: Plugin execution context with domain information
+
+        Returns:
+            PluginResult with HAProxy configuration snippet
+        """
+        if not self.enabled or not self.allowed_ips:
+            return PluginResult()
+
+        # Create space-separated list of IPs for ACL
+        ips_str = " ".join(self.allowed_ips)
+
+        # Generate HAProxy config snippet
+        haproxy_config = f"""# IP Whitelist - Only allow specific IPs
+    acl whitelisted_ip src {ips_str}
+    http-request deny deny_status {self.status_code} if !whitelisted_ip"""
+
+        return PluginResult(
+            haproxy_config=haproxy_config,
+            modified_easymapping=None,
+            metadata={
+                "domain": context.domain,
+                "allowed_ips": self.allowed_ips,
+                "status_code": self.status_code
+            }
+        )