Building out schema comparison mechanism

Which has led to a new wider hashing capability for the low level API. hashing makes it very easy to determine changes quickly, without having to run comparisons to discover changes, could really speed things up moving forward.

datamodel/low/base/xml.go

@@ -1,9 +1,12 @@
 package base
 
 import (
+	"crypto/sha256"
+	"fmt"
 	"github.com/pb33f/libopenapi/datamodel/low"
 	"github.com/pb33f/libopenapi/index"
 	"gopkg.in/yaml.v3"
+	"strings"
 )
 
 // XML represents a low-level representation of an XML object defined by all versions of OpenAPI.
@@ -32,3 +35,16 @@ func (x *XML) Build(root *yaml.Node, _ *index.SpecIndex) error {
 func (x *XML) GetExtensions() map[low.KeyReference[string]]low.ValueReference[any] {
 	return x.Extensions
 }
+
+// Hash generates a SHA256 hash of the XML object using properties
+func (x *XML) Hash() [32]byte {
+	// calculate a hash from every property.
+	d := []string{
+		x.Name.Value,
+		x.Namespace.Value,
+		x.Prefix.Value,
+		fmt.Sprintf("%v", x.Attribute.Value),
+		fmt.Sprintf("%v", x.Wrapped.Value),
+	}
+	return sha256.Sum256([]byte(strings.Join(d, "|")))
+}