Refactor Policy Enforcer to Policy Checker

- Renamed the `PolicyEnforcer` interface and related implementations to `PolicyChecker` for clarity and consistency.
- Updated configuration keys in YAML files to reflect the new `checkPolicy` terminology.
- Adjusted related code, tests, and documentation to support the new naming convention and ensure compatibility.
- Enhanced comments and examples for the `checkPolicy` configuration to improve usability.

pkg/plugin/implementation/opapolicychecker/cmd/plugin.go

@@ -0,0 +1,26 @@
+// Package main provides the plugin entry point for the OPA Policy Checker plugin.
+// This file is compiled as a Go plugin (.so) and loaded by beckn-onix at runtime.
+package main
+
+import (
+	"context"
+
+	"github.com/beckn-one/beckn-onix/pkg/plugin/definition"
+	"github.com/beckn-one/beckn-onix/pkg/plugin/implementation/opapolicychecker"
+)
+
+// provider implements the PolicyCheckerProvider interface for plugin loading.
+type provider struct{}
+
+// New creates a new PolicyChecker instance.
+func (p provider) New(ctx context.Context, cfg map[string]string) (definition.PolicyChecker, func(), error) {
+	checker, err := opapolicychecker.New(ctx, cfg)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return checker, checker.Close, nil
+}
+
+// Provider is the exported symbol that beckn-onix plugin manager looks up.
+var Provider = provider{}