fix(crd-upgrade-safety): Safely handle changes to description fields

Motivation:

When attempting to upgrade argocd-operator from v0.5.0 to v0.7.0, the upgrade process fails during the preflight CRD safety validation. The validation correctly detects that the `argocds.argoproj.io` CRD has been modified between the two versions.

The specific error reported is:

```
CustomResourceDefinition argocds.argoproj.io failed upgrade safety validation. "ChangeValidator" validation failed: version "v1alpha1", field "^.status.applicationController" has unknown change, refusing to determine that change is safe
```

However, changes between the CRD versions in this instance are limited to non-functional updates in the description fields of various properties (e.g., status.applicationController).`ChangeValidator` lacks a specific rule to classify a description-only update as safe, which blocks legitimate and otherwise safe operator upgrades.

Solution:

This PR enhances the CRD upgrade safety validation logic to correctly handle changes to description fields by introducing a new `ChangeValidation` check for `Description`, and registering the check by adding it to the default list of `ChangeValidations` used by `ChangeValidator`.

Result:

Non-functional updates to documentation fields are now deemed safe(which resolves the upgrade failure for argocd-operator from v0.5.0 to v0.7.0)

Author: anik120

internal/operator-controller/rukpak/preflights/crdupgradesafety/checks.go

@@ -242,3 +242,13 @@ func Type(diff FieldDiff) (bool, error) {
 
 	return isHandled(diff, reset), err
 }
+
+// Description changes are considered safe and non-breaking.
+func Description(diff FieldDiff) (bool, error) {
+	reset := func(diff FieldDiff) FieldDiff {
+		diff.Old.Description = ""
+		diff.New.Description = ""
+		return diff
+	}
+	return isHandled(diff, reset), nil
+}

internal/operator-controller/rukpak/preflights/crdupgradesafety/checks_test.go

@@ -904,3 +904,105 @@ func TestType(t *testing.T) {
 		})
 	}
 }
+
+func TestDescription(t *testing.T) {
+	for _, tc := range []testcase{
+		{
+			name: "no diff, no error, handled",
+			diff: FieldDiff{
+				Old: &apiextensionsv1.JSONSchemaProps{
+					Description: "some field",
+				},
+				New: &apiextensionsv1.JSONSchemaProps{
+					Description: "some field",
+				},
+			},
+			err:     nil,
+			handled: true,
+		},
+		{
+			name: "description changed, no error, handled",
+			diff: FieldDiff{
+				Old: &apiextensionsv1.JSONSchemaProps{
+					Description: "old description",
+				},
+				New: &apiextensionsv1.JSONSchemaProps{
+					Description: "new description",
+				},
+			},
+			err:     nil,
+			handled: true,
+		},
+		{
+			name: "description added, no error, handled",
+			diff: FieldDiff{
+				Old: &apiextensionsv1.JSONSchemaProps{},
+				New: &apiextensionsv1.JSONSchemaProps{
+					Description: "a new description was added",
+				},
+			},
+			err:     nil,
+			handled: true,
+		},
+		{
+			name: "description removed, no error, handled",
+			diff: FieldDiff{
+				Old: &apiextensionsv1.JSONSchemaProps{
+					Description: "this description will be removed",
+				},
+				New: &apiextensionsv1.JSONSchemaProps{},
+			},
+			err:     nil,
+			handled: true,
+		},
+		{
+			name: "different field changed, no error, not handled",
+			diff: FieldDiff{
+				Old: &apiextensionsv1.JSONSchemaProps{
+					ID: "foo",
+				},
+				New: &apiextensionsv1.JSONSchemaProps{
+					ID: "bar",
+				},
+			},
+			err:     nil,
+			handled: false,
+		},
+		{
+			name: "different field changed with description, no error, not handled",
+			diff: FieldDiff{
+				Old: &apiextensionsv1.JSONSchemaProps{
+					ID:          "foo",
+					Description: "description",
+				},
+				New: &apiextensionsv1.JSONSchemaProps{
+					ID:          "bar",
+					Description: "description",
+				},
+			},
+			err:     nil,
+			handled: false,
+		},
+		{
+			name: "description and ID changed, no error, not handled",
+			diff: FieldDiff{
+				Old: &apiextensionsv1.JSONSchemaProps{
+					ID:          "foo",
+					Description: "old description",
+				},
+				New: &apiextensionsv1.JSONSchemaProps{
+					ID:          "bar",
+					Description: "new description",
+				},
+			},
+			err:     nil,
+			handled: false,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			handled, err := Description(tc.diff)
+			require.Equal(t, tc.err, err)
+			require.Equal(t, tc.handled, handled)
+		})
+	}
+}

internal/operator-controller/rukpak/preflights/crdupgradesafety/crdupgradesafety.go

@@ -31,6 +31,7 @@ type Preflight struct {
 
 func NewPreflight(crdCli apiextensionsv1client.CustomResourceDefinitionInterface, opts ...Option) *Preflight {
 	changeValidations := []ChangeValidation{
+		Description,
 		Enum,
 		Required,
 		Maximum,