rbd: add support for flattenMode option for replication

This commit adds support for flattenMode option
for replication.
If the flattenMode is set to "force" in
volumereplicationclass parameters, cephcsi will
add a task to flatten the image if it has parent.
This enable cephcsi to then mirror such images after
flattening them.
The error message when the image's parent is
in trash or unmirrored is improved as well.

Signed-off-by: Rakshith R <rar@redhat.com>

internal/csi-addons/rbd/replication_test.go

@@ -641,3 +641,69 @@ func Test_timestampFromString(t *testing.T) {
 		})
 	}
 }
+
+func Test_getFlattenMode(t *testing.T) {
+	t.Parallel()
+	type args struct {
+		ctx        context.Context
+		parameters map[string]string
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    corerbd.FlattenMode
+		wantErr bool
+	}{
+		{
+			name: "flattenMode option not set",
+			args: args{
+				ctx:        context.TODO(),
+				parameters: map[string]string{},
+			},
+			want: corerbd.FlattenModeNever,
+		},
+		{
+			name: "flattenMode option set to never",
+			args: args{
+				ctx: context.TODO(),
+				parameters: map[string]string{
+					flattenModeKey: string(corerbd.FlattenModeNever),
+				},
+			},
+			want: corerbd.FlattenModeNever,
+		},
+		{
+			name: "flattenMode option set to force",
+			args: args{
+				ctx: context.TODO(),
+				parameters: map[string]string{
+					flattenModeKey: string(corerbd.FlattenModeForce),
+				},
+			},
+			want: corerbd.FlattenModeForce,
+		},
+
+		{
+			name: "flattenMode option set to invalid value",
+			args: args{
+				ctx: context.TODO(),
+				parameters: map[string]string{
+					flattenModeKey: "invalid123",
+				},
+			},
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			got, err := getFlattenMode(tt.args.ctx, tt.args.parameters)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("getFlattenMode() error = %v, wantErr %v", err, tt.wantErr)
+			}
+			if !tt.wantErr && !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("getFlattenMode() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}