Update validation for API Priority and Fairness

This PR fixes oversights and adds validation that rejects writes
of wrong Spec values for the four mandatory objects.

pkg/apis/flowcontrol/internalbootstrap/default-internal.go

@@ -0,0 +1,66 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+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
+
+    http://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 internalbootstrap
+
+import (
+	fcv1a1 "k8s.io/api/flowcontrol/v1alpha1"
+	"k8s.io/apimachinery/pkg/conversion"
+	"k8s.io/apiserver/pkg/apis/flowcontrol/bootstrap"
+	"k8s.io/kubernetes/pkg/apis/flowcontrol"
+	"k8s.io/kubernetes/pkg/apis/flowcontrol/install"
+)
+
+// MandatoryFlowSchemas holds the untyped renditions of the mandatory
+// flow schemas.  In this map the key is the schema's name and the
+// value is the `*FlowSchema`.  Nobody should mutate anything
+// reachable from this map.
+var MandatoryFlowSchemas = internalizeFSes(bootstrap.MandatoryFlowSchemas)
+
+// MandatoryPriorityLevels holds the untyped renditions of the
+// mandatory priority level configuration objects.  In this map the
+// key is the object's name and the value is the
+// `*PriorityLevelConfiguration`.  Nobody should mutate anything
+// reachable from this map.
+var MandatoryPriorityLevels = internalizePLs(bootstrap.MandatoryPriorityLevelConfigurations)
+
+func internalizeFSes(exts []*fcv1a1.FlowSchema) map[string]*flowcontrol.FlowSchema {
+	ans := make(map[string]*flowcontrol.FlowSchema, len(exts))
+	converter := install.GetTheScheme().Converter()
+	for _, ext := range exts {
+		var untyped flowcontrol.FlowSchema
+		err := converter.Convert(ext, &untyped, 0, &conversion.Meta{})
+		if err != nil {
+			panic(err)
+		}
+		ans[ext.Name] = &untyped
+	}
+	return ans
+}
+
+func internalizePLs(exts []*fcv1a1.PriorityLevelConfiguration) map[string]*flowcontrol.PriorityLevelConfiguration {
+	ans := make(map[string]*flowcontrol.PriorityLevelConfiguration, len(exts))
+	converter := install.GetTheScheme().Converter()
+	for _, ext := range exts {
+		var untyped flowcontrol.PriorityLevelConfiguration
+		err := converter.Convert(ext, &untyped, 0, &conversion.Meta{})
+		if err != nil {
+			panic(err)
+		}
+		ans[ext.Name] = &untyped
+	}
+	return ans
+}