Enhance support for multi-tenancy (#1371)

This enhances every ARC controller and the various K8s custom resources so that the user can now configure a custom GitHub API credentials (that is different from the default one configured per the ARC instance).

Ref https://github.com/actions-runner-controller/actions-runner-controller/issues/1067#issuecomment-1043716646

controllers/new_runner_pod_test.go

@@ -10,7 +10,9 @@ import (
 	"k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/types"
 	clientgoscheme "k8s.io/client-go/kubernetes/scheme"
+	"sigs.k8s.io/controller-runtime/pkg/client"
 )
 
 func newWorkGenericEphemeralVolume(t *testing.T, storageReq string) corev1.Volume {
@@ -1129,13 +1131,20 @@ func TestNewRunnerPodFromRunnerController(t *testing.T) {
 
 	for i := range testcases {
 		tc := testcases[i]
+
+		rr := &testResourceReader{
+			objects: map[types.NamespacedName]client.Object{},
+		}
+
+		multiClient := NewMultiGitHubClient(rr, &github.Client{GithubBaseURL: githubBaseURL})
+
 		t.Run(tc.description, func(t *testing.T) {
 			r := &RunnerReconciler{
 				RunnerImage:            defaultRunnerImage,
 				RunnerImagePullSecrets: defaultRunnerImagePullSecrets,
 				DockerImage:            defaultDockerImage,
 				DockerRegistryMirror:   defaultDockerRegistryMirror,
-				GitHubClient:           &github.Client{GithubBaseURL: githubBaseURL},
+				GitHubClient:           multiClient,
 				Scheme:                 scheme,
 			}
 			got, err := r.newPod(tc.runner)