check for correct kustomization in multi-doc yaml

Signed-off-by: Somtochi Onyekwere <somtochionyekwere@gmail.com>

internal/build/testdata/local-kustomization/different-name.yaml

@@ -0,0 +1,7 @@
+apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
+kind: Kustomization
+metadata:
+  name: infra
+  namespace: flux-system
+spec:
+  path: "./clusters/test-build"

internal/build/testdata/local-kustomization/multi-doc-valid.yaml

@@ -0,0 +1,32 @@
+---
+apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
+kind: Kustomization
+metadata:
+  name: infra-namespace
+  namespace: flux-system
+  labels:
+    component.kutara.io/part-of: definitions
+spec:
+  path: "./k8s/base/infra"
+  prune: true
+---
+---
+apiVersion: source.toolkit.fluxcd.io/v1beta2
+kind: GitRepository
+metadata:
+  name: podinfo
+  namespace: flux-system
+spec:
+  interval: 30s
+  ref:
+    branch: master
+  url: https://github.com/stefanprodan/podinfo
+---
+apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
+kind: Kustomization
+metadata:
+  name: podinfo
+  namespace: flux-system
+spec:
+  path: "./clusters/test-build"
+---

internal/build/testdata/local-kustomization/no-ns.yaml

@@ -0,0 +1,6 @@
+apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
+kind: Kustomization
+metadata:
+  name: podinfo
+spec:
+  path: "./clusters/test-build"

internal/build/testdata/local-kustomization/valid.yaml

@@ -0,0 +1,7 @@
+apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
+kind: Kustomization
+metadata:
+  name: podinfo
+  namespace: flux-system
+spec:
+  path: "./clusters/test-build"