NOISSUE - Revert removal of notifier interface (absmach#2643)

Signed-off-by: Felix Gateru <[email protected]>

.github/workflows/check-generated-files.yml

@@ -66,6 +66,7 @@ jobs:
               - "certs/pki/vault.go"
               - "certs/service.go"
               - "journal/journal.go"
+              - "consumers/notifier.go"
 
       - name: Set up protoc
         if: steps.changes.outputs.proto == 'true'
@@ -162,6 +163,7 @@ jobs:
           mv ./pkg/events/mocks/publisher.go ./pkg/events/mocks/publisher.go.tmp
           mv ./pkg/policies/mocks/evaluator.go ./pkg/policies/mocks/evaluator.go.tmp
           mv ./pkg/policies/mocks/service.go ./pkg/policies/mocks/service.go.tmp
+          mv ./consumers/mocks/notifier.go ./consumers/mocks/notifier.go.tmp
 
           make mocks
 
@@ -220,3 +222,4 @@ jobs:
           check_mock_changes ./pkg/events/mocks/publisher.go " ./pkg/events/mocks/publisher.go"
           check_mock_changes ./pkg/policies/mocks/evaluator.go " ./pkg/policies/mocks/evaluator.go"
           check_mock_changes ./pkg/policies/mocks/service.go " ./pkg/policies/mocks/service.go"
+          check_mock_changes ./consumers/mocks/notifier.go " ./consumers/mocks/notifier.go"

consumers/notifier.go

@@ -0,0 +1,22 @@
+// Copyright (c) Abstract Machines
+// SPDX-License-Identifier: Apache-2.0
+
+package consumers
+
+import (
+	"errors"
+
+	"github.com/absmach/supermq/pkg/messaging"
+)
+
+// ErrNotify wraps sending notification errors.
+var ErrNotify = errors.New("error sending notification")
+
+// Notifier represents an API for sending notification.
+//
+//go:generate mockery --name Notifier --output=./mocks --filename notifier.go --quiet --note "Copyright (c) Abstract Machines"
+type Notifier interface {
+	// Notify method is used to send notification for the
+	// received message to the provided list of receivers.
+	Notify(from string, to []string, msg *messaging.Message) error
+}