Add migration.{Converter,Source,Target} interfaces

Signed-off-by: Alper Rifat Ulucinar <ulucinar@users.noreply.github.com>

pkg/migration/interfaces.go

@@ -0,0 +1,34 @@
+/*
+Copyright 2022 Upbound Inc.
+*/
+
+package migration
+
+import (
+	"github.com/crossplane/crossplane-runtime/pkg/resource"
+	v1 "github.com/crossplane/crossplane/apis/apiextensions/v1"
+)
+
+type Converter interface {
+	// Resources takes a managed resource and returns zero or more managed
+	// resources to be created.
+	Resources(mg resource.Managed) ([]resource.Managed, error)
+
+	// ComposedTemplates takes a ComposedTemplate entry and returns zero or more
+	// ComposedTemplate with the new shape, including the necessary changes in
+	// its patches. Conversion of the v1.ComposedTemplate.Bases is handled
+	// via Converter.Resources and Converter.ComposedTemplates must only
+	// convert the other fields (`Patches`, `ConnectionDetails`, etc.)
+	ComposedTemplates(cmp v1.ComposedTemplate, convertedBase ...*v1.ComposedTemplate) error
+}
+
+type Source interface {
+	HasNext() (bool, error)
+	Next() (UnstructuredWithMetadata, error)
+}
+
+type Target interface {
+	Put(o UnstructuredWithMetadata) error
+	Patch(o UnstructuredWithMetadata) error
+	Delete(o UnstructuredWithMetadata) error
+}