resolved reqpreprocessing review comments

1. added logs for contextKey parsing and unmarshaling yml file.
2. resolved router test case issue.
2. resolved logger test case issues.

pkg/model/error_test.go

@@ -3,8 +3,8 @@ package model
 import (
 	"errors"
 	"fmt"
-	"testing"
 	"net/http"
+	"testing"
 
 	"github.com/stretchr/testify/assert"
 	"gopkg.in/yaml.v2"
@@ -198,3 +198,54 @@ func TestSchemaValidationErr_BecknError_NoErrors(t *testing.T) {
 		t.Errorf("beErr.Code = %s, want %s", beErr.Code, expectedCode)
 	}
 }
+
+func TestParseContextKey_ValidKeys(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected ContextKey
+	}{
+		{"message_id", ContextKeyMsgID},
+		{"subscriber_id", ContextKeySubscriberID},
+		{"model_id", ContextKeyModelID},
+	}
+
+	for _, tt := range tests {
+		key, err := ParseContextKey(tt.input)
+		if err != nil {
+			t.Errorf("unexpected error for input %s: %v", tt.input, err)
+		}
+		if key != tt.expected {
+			t.Errorf("expected %s, got %s", tt.expected, key)
+		}
+	}
+}
+
+func TestParseContextKey_InvalidKey(t *testing.T) {
+	_, err := ParseContextKey("invalid_key")
+	if err == nil {
+		t.Error("expected error for invalid context key, got nil")
+	}
+}
+
+func TestContextKey_UnmarshalYAML_Valid(t *testing.T) {
+	yamlData := []byte("message_id")
+	var key ContextKey
+
+	err := yaml.Unmarshal(yamlData, &key)
+	if err != nil {
+		t.Errorf("unexpected error: %v", err)
+	}
+	if key != ContextKeyMsgID {
+		t.Errorf("expected %s, got %s", ContextKeyMsgID, key)
+	}
+}
+
+func TestContextKey_UnmarshalYAML_Invalid(t *testing.T) {
+	yamlData := []byte("invalid_key")
+	var key ContextKey
+
+	err := yaml.Unmarshal(yamlData, &key)
+	if err == nil {
+		t.Error("expected error for invalid context key, got nil")
+	}
+}

pkg/model/model.go

@@ -42,6 +42,9 @@ const (
 type ContextKey string
 
 const (
+	// ContextKeyTxnID is the context key used to store and retrieve the transaction ID in a request context.
+	ContextKeyTxnID ContextKey = "transaction_id"
+
 	// ContextKeyMsgID is the context key used to store and retrieve the message ID in a request context.
 	ContextKeyMsgID ContextKey = "message_id"
 
@@ -52,6 +55,38 @@ const (
 	ContextKeyModelID ContextKey = "model_id"
 )
 
+var contextKeys = map[string]ContextKey{
+	"message_id":    ContextKeyMsgID,
+	"subscriber_id": ContextKeySubscriberID,
+	"model_id":      ContextKeyModelID,
+}
+
+// ParseContextKey converts a string into a valid ContextKey.
+func ParseContextKey(v string) (ContextKey, error) {
+	key, ok := contextKeys[v]
+	if !ok {
+		return "", fmt.Errorf("invalid context key: %s", key)
+	}
+	return key, nil
+}
+
+// UnmarshalYAML ensures that only known context keys are accepted during YAML unmarshalling.
+func (k *ContextKey) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var keyStr string
+	if err := unmarshal(&keyStr); err != nil {
+		return err
+	}
+
+	parsedKey, err := ParseContextKey(keyStr)
+	if err != nil {
+		return err
+	}
+
+	*k = parsedKey
+	return nil
+
+}
+
 // Role defines the type of participant in the network.
 type Role string