Support for alternate http auth mechanisms (#291)

Fixes #290

Author: jake-scott

openapi3/security_scheme.go

@@ -115,7 +115,7 @@ func (ss *SecurityScheme) Validate(c context.Context) error {
 		switch scheme {
 		case "bearer":
 			hasBearerFormat = true
-		case "basic":
+		case "basic", "negotiate", "digest":
 		default:
 			return fmt.Errorf("Security scheme of type 'http' has invalid 'scheme' value '%s'", scheme)
 		}

openapi3/security_scheme_test.go

@@ -46,6 +46,26 @@ var securitySchemeExamples = []securitySchemeExample{
 `),
 		valid: true,
 	},
+	{
+		title: "Negotiate Authentication Sample",
+		raw: []byte(`
+{
+  "type": "http",
+  "scheme": "negotiate"
+}
+`),
+		valid: true,
+	},
+	{
+		title: "Unknown http Authentication Sample",
+		raw: []byte(`
+{
+  "type": "http",
+  "scheme": "notvalid"
+}
+`),
+		valid: false,
+	},
 	{
 		title: "API Key Sample",
 		raw: []byte(`