MG-3537 - Migrate Magistrala to ATOM for identity & authorization (#3532)

Signed-off-by: Arvindh <arvindh91@gmail.com>
Signed-off-by: dusan <borovcanindusan1@gmail.com>
Signed-off-by: Rodney Osodo <socials@rodneyosodo.com>
Co-authored-by: Dušan Borovčanin <dusan.borovcanin@absmach.eu>
Co-authored-by: Rodney Osodo <socials@rodneyosodo.com>
Co-authored-by: dusan <borovcanindusan1@gmail.com>

pkg/authn/atom/authn.go

@@ -0,0 +1,37 @@
+// Copyright (c) Abstract Machines
+// SPDX-License-Identifier: Apache-2.0
+
+package atom
+
+import (
+	"context"
+
+	atomcore "github.com/absmach/magistrala/internal/atom"
+	"github.com/absmach/magistrala/pkg/authn"
+	"github.com/absmach/magistrala/pkg/errors"
+	svcerr "github.com/absmach/magistrala/pkg/errors/service"
+)
+
+type authentication struct {
+	verifier *atomcore.TokenVerifier
+}
+
+var _ authn.Authentication = (*authentication)(nil)
+
+func NewAuthentication() authn.Authentication {
+	return authentication{verifier: atomcore.NewTokenVerifier(atomcore.LoadConfig())}
+}
+
+func (a authentication) Authenticate(ctx context.Context, token string) (authn.Session, error) {
+	claims, err := a.verifier.VerifyTokenClaims(ctx, token)
+	if err != nil {
+		return authn.Session{}, errors.Wrap(svcerr.ErrAuthentication, err)
+	}
+	return authn.Session{
+		Type:     authn.AccessToken,
+		UserID:   claims.SubjectID,
+		DomainID: claims.TenantID,
+		Role:     authn.UserRole,
+		Verified: true,
+	}, nil
+}