Add generic container executor

This executor based on kyaml.RunFns[1].
It allows to execute arbitrary container as RunFns function
and handle any input data as ExecutorBundle.
Be aware that runtimeutils.FunctionSpec used for version 0.4.1[2]
and it can be changed in the future. It means that yaml scheme
of executor can be changed during kyaml uplift.
This executor transforms executor yaml to RunFns function acceptable format.

[1] https://github.com/kubernetes-sigs/kustomize/blob/master/kyaml/runfn/runfn.go
[2] https://github.com/kubernetes-sigs/kustomize/blob/kyaml/v0.4.1/kyaml/fn/runtime/runtimeutil/functiontypes.go#L22

Change-Id: I9eb648783f1ed462d2b8359d9dc86320c4db2a83
Closes: #202
Closes: #369

pkg/api/v1alpha1/genericcontainer_types.go

@@ -0,0 +1,64 @@
+/*
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     https://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package v1alpha1
+
+import (
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"sigs.k8s.io/kustomize/kyaml/fn/runtime/runtimeutil"
+)
+
+// +kubebuilder:object:root=true
+
+// GenericContainer provides info about generic container
+type GenericContainer struct {
+	metav1.TypeMeta   `json:",inline"`
+	metav1.ObjectMeta `json:"metadata,omitempty"`
+	// If set to will print output of RunFns to Stdout
+	PrintOutput bool `json:"printOutput,omitempty"`
+	// Settings for for a container
+	Spec runtimeutil.FunctionSpec `json:"spec,omitempty"`
+	// Config for the RunFns function in a custom format
+	Config string `json:"config,omitempty"`
+}
+
+// DefaultGenericContainer can be used to safely unmarshal GenericContainer object without nil pointers
+func DefaultGenericContainer() *GenericContainer {
+	return &GenericContainer{
+		Spec: runtimeutil.FunctionSpec{},
+	}
+}
+
+// DeepCopyInto is copying the receiver, writing into out. in must be non-nil.
+func (in *GenericContainer) DeepCopyInto(out *GenericContainer) {
+	*out = *in
+	out.TypeMeta = in.TypeMeta
+	in.ObjectMeta.DeepCopyInto(&out.ObjectMeta)
+
+	out.Spec = in.Spec
+	out.Spec.Container = in.Spec.Container
+	out.Spec.Container.Network = in.Spec.Container.Network
+	if in.Spec.Container.StorageMounts != nil {
+		in, out := &in.Spec.Container.StorageMounts, &out.Spec.Container.StorageMounts
+		*out = make([]runtimeutil.StorageMount, len(*in))
+		copy(*out, *in)
+	}
+	out.Spec.Starlark = in.Spec.Starlark
+	out.Spec.Exec = in.Spec.Exec
+	if in.Spec.StorageMounts != nil {
+		in, out := &in.Spec.StorageMounts, &out.Spec.StorageMounts
+		*out = make([]runtimeutil.StorageMount, len(*in))
+		copy(*out, *in)
+	}
+}