chore: apply review feedback

Signed-off-by: doxsch <28098153+doxsch@users.noreply.github.com>

Author: doxsch

example/inline-templates/composition.yaml

@@ -16,4 +16,4 @@ spec:
         kind: GoTemplate
         source: Inline
         inline:
-          templates: []
+          templates: [] # Kustomize will add the templates here

input/v1beta1/input.go

@@ -49,7 +49,8 @@ const (
 	EnvironmentSource TemplateSource = "Environment"
 )
 
-// TemplateSourceInline defines the structure of the inline source.
+// TemplateSourceInline defines the structure of the inline source. Allows specifying either a single inline template or multiple templates, but not both.
+// +kubebuilder:validation:XValidation:rule="(has(self.template) ? 1 : 0) + (has(self.templates) ? 1 : 0) == 1",message="Exactly one of 'template' or 'templates' must be set"
 type TemplateSourceInline struct {
 	Template  string   `json:"template,omitempty"`
 	Templates []string `json:"templates,omitempty"`

package/input/gotemplating.fn.crossplane.io_gotemplates.yaml

@@ -63,6 +63,10 @@ spec:
                   type: string
                 type: array
             type: object
+            x-kubernetes-validations:
+            - message: Exactly one of 'template' or 'templates' must be set
+              rule: '(has(self.template) ? 1 : 0) + (has(self.templates) ? 1 : 0)
+                == 1'
           kind:
             description: |-
               Kind is a string value representing the REST resource this object represents.

template.go

@@ -5,8 +5,6 @@ import (
 	"path/filepath"
 	"strings"
 
-	"google.golang.org/protobuf/types/known/structpb"
-
 	"github.com/crossplane-contrib/function-go-templating/input/v1beta1"
 	"google.golang.org/protobuf/types/known/structpb"