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/discriminator.go

@@ -4,7 +4,10 @@
 package base
 
 import (
+	"crypto/sha256"
 	"github.com/pb33f/libopenapi/datamodel/low"
+	"sort"
+	"strings"
 )
 
 // Discriminator is only used by OpenAPI 3+ documents, it represents a polymorphic discriminator used for schemas
@@ -29,3 +32,21 @@ func (d *Discriminator) FindMappingValue(key string) *low.ValueReference[string]
 	}
 	return nil
 }
+
+// Hash will return a consistent SHA256 Hash of the Discriminator object
+func (d *Discriminator) Hash() [32]byte {
+
+	// calculate a hash from every property.
+	f := []string{d.PropertyName.Value}
+
+	propertyKeys := make([]string, 0, len(d.Mapping))
+	for i := range d.Mapping {
+		propertyKeys = append(propertyKeys, i.Value)
+	}
+	sort.Strings(propertyKeys)
+	for k := range propertyKeys {
+		prop := d.FindMappingValue(propertyKeys[k])
+		f = append(f, prop.Value)
+	}
+	return sha256.Sum256([]byte(strings.Join(f, "|")))
+}