Cast parent resource type

[scothis]

A CastParent reconciler casts the ParentReconciler's type by projecting the
resource data onto a new struct. Casting the parent resource is
useful to create cross cutting reconcilers that can operate on common
portion of multiple parent resources, commonly referred to as a duck type.

JSON encoding is used as the intermediate representation. Operations on
a cast parent are read-only. Attempts to mutate the parent will result
in the reconciler erring.

func FunctionReconciler(c reconcilers.Config) *reconcilers.ParentReconciler {
	c.Log = c.Log.WithName("Function")

	return &reconcilers.ParentReconciler{
		Type: &buildv1alpha1.Function{},
		Reconciler: reconcilers.Sequence{
			&reconcilers.CastParent{
				Type: &duckv1alpha1.ImageRef{},
				Reconciler: &reconcilers.SyncReconciler{
					Sync: func(ctx context.Context, parent *duckv1alpha1.ImageRef) error {
						// do something with the duckv1alpha1.ImageRef instead of a buildv1alpha1.Function
						return nil
					},
					Config: c,
				},
			},
			FunctionChildImageReconciler(c),
		},

		Config: c,
	}
}

Signed-off-by: Scott Andrews andrewssc@vmware.com

[codecov]

Codecov Report

Merging #51 (d566213) into main (2db5e1f) will increase coverage by 1.27%.
The diff coverage is 88.09%.

@@            Coverage Diff             @@
##             main      #51      +/-   ##
==========================================
+ Coverage   61.38%   62.65%   +1.27%     
==========================================
  Files          11       11              
  Lines         606      640      +34     
==========================================
+ Hits          372      401      +29     
- Misses        226      231       +5     
  Partials        8        8              

Impacted Files	Coverage Δ
reconcilers/reconcilers.go	85.36% <88.09%> (-0.01%)	⬇️

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[glyn]

LGTM, just some commentary suggestions.