Update flagd injector and tests

Signed-off-by: Yosiah de Koeyer <dev@yosiahdekoeyer.dev>

Author: Y0sh1dk

internal/common/flagdinjector/flagdinjector.go

@@ -20,6 +20,7 @@ import (
 	"k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/util/intstr"
+	"k8s.io/utils/ptr"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 )
 
@@ -85,7 +86,14 @@ func (fi *FlagdContainerInjector) InjectFlagd(
 		flagdContainer.Resources.Limits = flagSourceConfig.Resources.Limits
 	}
 
-	addFlagdContainer(podSpec, flagdContainer)
+	// Handle standalone Flagd deployment as well as sidecar injection.
+	if len(podSpec.Containers) == 0 {
+		addFlagdContainer(podSpec, flagdContainer)
+	} else {
+		flagdContainer.RestartPolicy = ptr.To(corev1.ContainerRestartPolicyAlways)
+
+		addFlagdSidecarContainer(podSpec, flagdContainer)
+	}
 
 	return nil
 }
@@ -472,6 +480,16 @@ func (fi *FlagdContainerInjector) createConfigMap(ctx context.Context, namespace
 	return fi.Client.Create(ctx, cm)
 }
 
+func addFlagdSidecarContainer(spec *corev1.PodSpec, flagdContainer corev1.Container) {
+	for idx, container := range spec.InitContainers {
+		if container.Name == flagdContainer.Name {
+			spec.InitContainers[idx] = flagdContainer
+			return
+		}
+	}
+	spec.InitContainers = append(spec.InitContainers, flagdContainer)
+}
+
 func addFlagdContainer(spec *corev1.PodSpec, flagdContainer corev1.Container) {
 	for idx, container := range spec.Containers {
 		if container.Name == flagdContainer.Name {