Force Draft version of JsonSchema (#221)

* Force Draft version of JsonSchema
* Add test validating using CRD that misses explicit draft version

acceptance.bats

@@ -340,3 +340,8 @@ resetCacheFolder() {
   run xmllint --noout --schema fixtures/junit.xsd output.xml
   [ "$status" -eq 0 ]
 }
+
+@test "passes when trying to use a CRD that does not have the JSONSchema set" {
+  run bash -c "bin/kubeconform -schema-location default -schema-location 'https://raw.githubusercontent.com/datreeio/CRDs-catalog/main/{{.Group}}/{{.ResourceKind}}_{{.ResourceAPIVersion}}.json' fixtures/httpproxy.yaml"
+  [ "$status" -eq 0 ]
+}

fixtures/httpproxy.yaml

@@ -0,0 +1,13 @@
+apiVersion: projectcontour.io/v1
+kind: HTTPProxy
+metadata:
+  name: basic
+spec:
+  virtualhost:
+    fqdn: foo-basic.example.com
+  routes:
+    - conditions:
+        - prefix: /
+      services:
+        - name: s1
+          port: 80

pkg/validator/validator.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"strings"
 
 	jsonschema "github.com/santhosh-tekuri/jsonschema/v5"
 	_ "github.com/santhosh-tekuri/jsonschema/v5/httploader"
@@ -254,7 +255,12 @@ func downloadSchema(registries []registry.Registry, kind, version, k8sVersion st
 	for _, reg := range registries {
 		path, schemaBytes, err = reg.DownloadSchema(kind, version, k8sVersion)
 		if err == nil {
-			schema, err := jsonschema.CompileString(path, string(schemaBytes))
+			c := jsonschema.NewCompiler()
+			c.Draft = jsonschema.Draft4
+			if err := c.AddResource(path, strings.NewReader(string(schemaBytes))); err != nil {
+				continue
+			}
+			schema, err := c.Compile(path)
 			// If we got a non-parseable response, we try the next registry
 			if err != nil {
 				continue