Add snapshotted mapping configuration sources

internal/engine/source_value.go

@@ -0,0 +1,19 @@
+package engine
+
+func (issue *valueIssue) sourceDiagnostic(sourceID string) Diagnostic {
+	code := CodeSourceInvalid
+	message := "mapping source has an unsupported value"
+	switch issue.kind {
+	case valueDepthLimit:
+		code, message = CodeSourceLimitExceeded, "mapping source exceeds the depth limit"
+	case valueNodeLimit:
+		code, message = CodeSourceLimitExceeded, "mapping source exceeds the node limit"
+	case valueByteLimit:
+		code, message = CodeSourceLimitExceeded, "mapping source exceeds the string-byte limit"
+	case valueNonFinite:
+		message = "mapping source float must be finite"
+	case valueCycle:
+		message = "mapping source values must not contain cycles"
+	}
+	return Diagnostic{Code: code, Severity: SeverityError, Path: issue.path.clone(), Message: message, Primary: &Location{SourceID: sourceID}}
+}