cli: fix upgrades when using outdated Kubernetes patch version (#2718)

* Fix missing image for Constellation operators in our Helm charts if the desired Kubernetes patch version is no longer supported (but Kubernetes upgrades are skipped)
* Correctly unmarshal Kubernetes Components list if the list uses an old format

---------

Signed-off-by: Daniel Weiße <dw@edgeless.systems>

internal/versions/components/components.go

@@ -8,6 +8,7 @@ package components
 
 import (
 	"crypto/sha256"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"strings"
@@ -16,6 +17,53 @@ import (
 // Components is a list of Kubernetes components.
 type Components []*Component
 
+type legacyComponent struct {
+	URL         string `json:"URL,omitempty"`
+	Hash        string `json:"Hash,omitempty"`
+	InstallPath string `json:"InstallPath,omitempty"`
+	Extract     bool   `json:"Extract,omitempty"`
+}
+
+// UnmarshalJSON implements a custom JSON unmarshaler to ensure backwards compatibility
+// with older components lists which had a different format for all keys.
+func (c *Components) UnmarshalJSON(b []byte) error {
+	var legacyComponents []*legacyComponent
+	if err := json.Unmarshal(b, &legacyComponents); err != nil {
+		return err
+	}
+	var components []*Component
+	if err := json.Unmarshal(b, &components); err != nil {
+		return err
+	}
+
+	if len(legacyComponents) != len(components) {
+		return errors.New("failed to unmarshal data: inconsistent number of components in list") // just a check, should never happen
+	}
+
+	// If a value is not set in the new format,
+	// it might have been set in the old format.
+	// In this case, we copy the value from the old format.
+	comps := make(Components, len(components))
+	for idx := 0; idx < len(components); idx++ {
+		comps[idx] = components[idx]
+		if comps[idx].Url == "" {
+			comps[idx].Url = legacyComponents[idx].URL
+		}
+		if comps[idx].Hash == "" {
+			comps[idx].Hash = legacyComponents[idx].Hash
+		}
+		if comps[idx].InstallPath == "" {
+			comps[idx].InstallPath = legacyComponents[idx].InstallPath
+		}
+		if !comps[idx].Extract {
+			comps[idx].Extract = legacyComponents[idx].Extract
+		}
+	}
+
+	*c = comps
+	return nil
+}
+
 // GetHash returns the hash over all component hashes.
 func (c Components) GetHash() string {
 	sha := sha256.New()