Move manifest unit tests to package manifest_test

This prevents an import cycle in tests: with the new Helm deployer
mocks, having manifest unit tests in package `manifest` would lead to:
```
package github.com/rancher/fleet/internal/manifest
        imports github.com/rancher/fleet/internal/mocks
        imports github.com/rancher/fleet/internal/helmdeployer
        imports github.com/rancher/fleet/internal/manifest: import cycle not allowed in test
```

internal/manifest/manifest.go

@@ -109,10 +109,10 @@ func (m *Manifest) ID() (string, error) {
 	if err != nil {
 		return "", err
 	}
-	return toSHA256ID(shasum), nil
+	return ToSHA256ID(shasum), nil
 }
 
-// toSHA256ID generates a valid Kubernetes name (max length of 64) from a provided SHA256 sum
-func toSHA256ID(shasum string) string {
+// ToSHA256ID generates a valid Kubernetes name (max length of 64) from a provided SHA256 sum
+func ToSHA256ID(shasum string) string {
 	return ("s-" + shasum)[:63]
 }

internal/manifest/store.go

@@ -14,12 +14,12 @@ import (
 
 func NewStore(client client.Client) *ContentStore {
 	return &ContentStore{
-		client: client,
+		Client: client,
 	}
 }
 
 type ContentStore struct {
-	client client.Client
+	Client client.Client
 }
 
 // Store stores the manifest as a content resource.
@@ -30,7 +30,7 @@ func (c *ContentStore) Store(ctx context.Context, manifest *Manifest) error {
 		return err
 	}
 
-	if err := c.client.Get(ctx, types.NamespacedName{Name: id}, &fleet.Content{}); err != nil && !apierrors.IsNotFound(err) {
+	if err := c.Client.Get(ctx, types.NamespacedName{Name: id}, &fleet.Content{}); err != nil && !apierrors.IsNotFound(err) {
 		return err
 	} else if err == nil {
 		return nil
@@ -55,7 +55,7 @@ func (c *ContentStore) createContents(ctx context.Context, id string, manifest *
 		return err
 	}
 
-	err = c.client.Create(ctx, &fleet.Content{
+	err = c.Client.Create(ctx, &fleet.Content{
 		ObjectMeta: metav1.ObjectMeta{
 			Name: id,
 		},

internal/manifest/store_test.go

@@ -1,4 +1,4 @@
-package manifest
+package manifest_test
 
 import (
 	"bytes"
@@ -11,14 +11,15 @@ import (
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/types"
 
+	"github.com/rancher/fleet/internal/manifest"
 	"github.com/rancher/fleet/internal/mocks"
 	fleet "github.com/rancher/fleet/pkg/apis/fleet.cattle.io/v1alpha1"
 )
 
-func testManifest(t *testing.T, data string) *Manifest {
+func testManifest(t *testing.T, data string) *manifest.Manifest {
 	t.Helper()
 
-	m, err := FromJSON([]byte(data), "")
+	m, err := manifest.FromJSON([]byte(data), "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -35,7 +36,7 @@ func Test_contentStore_Store(t *testing.T) {
 	resources := `{"resources": [{"name": "foo", "content": "bar"}]}`
 	checksum := "752ebbb975f52eea5e87950ef2ca5de4055de3c68a17f54d94527d7fd79c21fd"
 	type args struct {
-		manifest *Manifest
+		manifest *manifest.Manifest
 		cached   bool
 	}
 	tests := []struct {
@@ -48,23 +49,23 @@ func Test_contentStore_Store(t *testing.T) {
 			args: args{
 				manifest: testManifest(t, resources),
 			},
-			want: toSHA256ID(checksum),
+			want: manifest.ToSHA256ID(checksum),
 		},
 		{
 			name: "existing manifest",
 			args: args{
 				manifest: testManifest(t, resources),
 				cached:   true,
 			},
-			want: toSHA256ID(checksum),
+			want: manifest.ToSHA256ID(checksum),
 		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			ctrl := gomock.NewController(t)
 			client := mocks.NewMockClient(ctrl)
 
-			store := &ContentStore{client}
+			store := &manifest.ContentStore{client}
 			ctx := context.TODO()
 			nsn := types.NamespacedName{Name: tt.want}