Implement Policy Enforcer Plugin

- Added a new Policy Enforcer plugin to evaluate incoming messages against OPA policies.
- Configurable via YAML with options for policy sources, actions, and query.
- Integrated into existing configuration files for BAP and BPP.
- Updated related tests and documentation for the new functionality.
- Enhanced plugin manager to support Policy Enforcer instantiation.

go.mod

@@ -1,6 +1,6 @@
 module github.com/beckn-one/beckn-onix
 
-go 1.24.0
+go 1.24.6
 
 require (
 	github.com/santhosh-tekuri/jsonschema/v6 v6.0.1
@@ -22,16 +22,20 @@ require github.com/zenazn/pkcs7pad v0.0.0-20170308005700-253a5b1f0e03
 require golang.org/x/text v0.33.0 // indirect
 
 require (
+	github.com/agnivade/levenshtein v1.2.1 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cenkalti/backoff/v4 v4.3.0 // indirect
 	github.com/cenkalti/backoff/v5 v5.0.3 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.4.0 // indirect
 	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
 	github.com/go-jose/go-jose/v4 v4.1.3 // indirect
 	github.com/go-logr/logr v1.4.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/go-openapi/jsonpointer v0.21.0 // indirect
 	github.com/go-openapi/swag v0.23.0 // indirect
+	github.com/gobwas/glob v0.2.3 // indirect
+	github.com/goccy/go-json v0.10.5 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.27.7 // indirect
 	github.com/hashicorp/errwrap v1.1.0 // indirect
 	github.com/hashicorp/go-multierror v1.1.1 // indirect
@@ -41,33 +45,52 @@ require (
 	github.com/hashicorp/go-sockaddr v1.0.2 // indirect
 	github.com/hashicorp/hcl v1.0.0 // indirect
 	github.com/josharian/intern v1.0.0 // indirect
+	github.com/lestrrat-go/blackmagic v1.0.4 // indirect
+	github.com/lestrrat-go/dsig v1.0.0 // indirect
+	github.com/lestrrat-go/dsig-secp256k1 v1.0.0 // indirect
+	github.com/lestrrat-go/httpcc v1.0.1 // indirect
+	github.com/lestrrat-go/httprc/v3 v3.0.2 // indirect
+	github.com/lestrrat-go/jwx/v3 v3.0.13 // indirect
+	github.com/lestrrat-go/option/v2 v2.0.0 // indirect
 	github.com/mailru/easyjson v0.7.7 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
-	github.com/matttproud/golang_protobuf_extensions/v2 v2.0.0 // indirect
 	github.com/mitchellh/go-homedir v1.1.0 // indirect
 	github.com/mitchellh/mapstructure v1.5.0 // indirect
 	github.com/mohae/deepcopy v0.0.0-20170929034955-c48cc78d4826 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/oasdiff/yaml v0.0.0-20250309154309-f31be36b4037 // indirect
 	github.com/oasdiff/yaml3 v0.0.0-20250309153720-d2182401db90 // indirect
 	github.com/perimeterx/marshmallow v1.1.5 // indirect
-	github.com/prometheus/client_model v0.6.0 // indirect
-	github.com/prometheus/common v0.45.0 // indirect
-	github.com/prometheus/procfs v0.12.0 // indirect
+	github.com/prometheus/client_model v0.6.2 // indirect
+	github.com/prometheus/common v0.66.1 // indirect
+	github.com/prometheus/procfs v0.17.0 // indirect
+	github.com/rcrowley/go-metrics v0.0.0-20250401214520-65e299d6c5c9 // indirect
 	github.com/redis/go-redis/extra/rediscmd/v9 v9.16.0 // indirect
 	github.com/ryanuber/go-glob v1.0.0 // indirect
+	github.com/segmentio/asm v1.2.1 // indirect
+	github.com/sirupsen/logrus v1.9.4 // indirect
+	github.com/tchap/go-patricia/v2 v2.3.3 // indirect
+	github.com/valyala/fastjson v1.6.7 // indirect
+	github.com/vektah/gqlparser/v2 v2.5.31 // indirect
 	github.com/woodsbury/decimal128 v1.3.0 // indirect
+	github.com/xeipuuv/gojsonpointer v0.0.0-20190905194746-02993c407bfb // indirect
+	github.com/xeipuuv/gojsonreference v0.0.0-20180127040603-bd5ef7bd5415 // indirect
+	github.com/yashtewari/glob-intersection v0.2.0 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
-	go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc v0.16.0 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.39.0 // indirect
-	go.opentelemetry.io/otel/log v0.16.0 // indirect
 	go.opentelemetry.io/proto/otlp v1.9.0 // indirect
+	go.yaml.in/yaml/v2 v2.4.2 // indirect
+	go.yaml.in/yaml/v3 v3.0.4 // indirect
 	golang.org/x/net v0.49.0 // indirect
+	golang.org/x/sync v0.19.0 // indirect
 	golang.org/x/sys v0.40.0 // indirect
-	golang.org/x/time v0.0.0-20200416051211-89c76fbcd5d1 // indirect
+	golang.org/x/time v0.14.0 // indirect
 	google.golang.org/genproto/googleapis/api v0.0.0-20260128011058-8636f8732409 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20260128011058-8636f8732409 // indirect
 	google.golang.org/protobuf v1.36.11 // indirect
+	gopkg.in/ini.v1 v1.67.1 // indirect
+	sigs.k8s.io/yaml v1.6.0 // indirect
 )
 
 require (
@@ -76,16 +99,19 @@ require (
 	github.com/hashicorp/go-retryablehttp v0.7.7
 	github.com/hashicorp/vault/api v1.16.0
 	github.com/jsonata-go/jsonata v0.0.0-20250709164031-599f35f32e5f
-	github.com/prometheus/client_golang v1.18.0
+	github.com/open-policy-agent/opa v1.13.2
+	github.com/prometheus/client_golang v1.23.2
 	github.com/rabbitmq/amqp091-go v1.10.0
 	github.com/redis/go-redis/extra/redisotel/v9 v9.16.0
 	github.com/redis/go-redis/v9 v9.16.0
 	github.com/rs/zerolog v1.34.0
 	go.opentelemetry.io/contrib/instrumentation/runtime v0.64.0
 	go.opentelemetry.io/otel v1.40.0
+	go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc v0.16.0
 	go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc v1.39.0
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.39.0
 	go.opentelemetry.io/otel/exporters/prometheus v0.46.0
+	go.opentelemetry.io/otel/log v0.16.0
 	go.opentelemetry.io/otel/metric v1.40.0
 	go.opentelemetry.io/otel/sdk v1.40.0
 	go.opentelemetry.io/otel/sdk/log v0.16.0