Add single-source loading and version checks

records.go

@@ -72,6 +72,16 @@ const (
 	CodeDecodeText         Code = "decode.text"
 	CodeDecodeUnknownField Code = "decode.unknown_field"
 	CodeDecodeArrayLength  Code = "decode.array_length"
+
+	CodeOptionsInvalid     Code = "options.invalid"
+	CodeOptionsUnavailable Code = "options.unavailable"
+
+	CodeImportDisabled Code = "import.disabled"
+
+	CodeVersionType       Code = "version.type"
+	CodeVersionError      Code = "version.error"
+	CodeVersionWarning    Code = "version.warning"
+	CodeVersionHookFailed Code = "version.hook_failed"
 )
 
 // Location identifies a position in a configuration source. Zero line and column