Auth: Move Service Account service to SignedInUser Interface (#73142)

* move service account service to identity interface

* Update pkg/services/auth/identity/requester.go

pkg/services/auth/identity/requester.go

@@ -1,6 +1,12 @@
 package identity
 
-import "github.com/grafana/grafana/pkg/models/roletype"
+import (
+	"errors"
+	"fmt"
+	"strconv"
+
+	"github.com/grafana/grafana/pkg/models/roletype"
+)
 
 const (
 	NamespaceUser           = "user"
@@ -10,6 +16,9 @@ const (
 	NamespaceRenderService  = "render"
 )
 
+var ErrNotIntIdentifier = errors.New("identifier is not an int64")
+var ErrIdentifierNotInitialized = errors.New("identifier is not initialized")
+
 type Requester interface {
 	// GetDisplayName returns the display name of the active entity.
 	// The display name is the name if it is set, otherwise the login or email.
@@ -50,3 +59,24 @@ type Requester interface {
 	// HasUniqueId returns true if the entity has a unique id
 	HasUniqueId() bool
 }
+
+// IntIdentifier converts a string identifier to an int64.
+// Applicable for users, service accounts, api keys and renderer service.
+// Errors if the identifier is not initialized or if namespace is not recognized.
+func IntIdentifier(namespace, identifier string) (int64, error) {
+	switch namespace {
+	case NamespaceUser, NamespaceAPIKey, NamespaceServiceAccount, NamespaceRenderService:
+		id, err := strconv.ParseInt(identifier, 10, 64)
+		if err != nil {
+			return 0, fmt.Errorf("unrecognized format for valid namespace %s: %w", namespace, err)
+		}
+
+		if id < 1 {
+			return 0, ErrIdentifierNotInitialized
+		}
+
+		return id, nil
+	}
+
+	return 0, ErrNotIntIdentifier
+}