common/ImageType: move to the store package

This is now only used for marshalling in the store, so keep the logic
where it is used.

Signed-off-by: Tom Gundersen <teg@jklm.no>

internal/store/json_test.go

@@ -0,0 +1,23 @@
+package store
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestImageType_UnmarshalJSON(t *testing.T) {
+	dict := struct {
+		ImageTypes []imageType `json:"image_types"`
+	}{}
+	input := `{"image_types":["qcow2", "Azure"]}`
+	err := json.Unmarshal([]byte(input), &dict)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if dict.ImageTypes[0] != Qcow2Generic {
+		t.Fatal("failed to umarshal image type qcow2; got tag:", dict.ImageTypes[0])
+	}
+	if dict.ImageTypes[1] != Azure {
+		t.Fatal("failed to umarshal image type Azure; got tag:", dict.ImageTypes[0])
+	}
+}