osbuild: rename package to osbuild1

Preparing for version 2 of the manifest schema, which will be
implemented in a separate package (osbuild2) alongside the original.

internal/osbuild1/files_source.go

@@ -0,0 +1,16 @@
+package osbuild1
+
+type Secret struct {
+	Name string `json:"name,omitempty"`
+}
+type FileSource struct {
+	URL     string  `json:"url"`
+	Secrets *Secret `json:"secrets,omitempty"`
+}
+
+// The FilesSourceOptions specifies a custom script to run in the image
+type FilesSource struct {
+	URLs map[string]FileSource `json:"urls"`
+}
+
+func (FilesSource) isSource() {}