Add support for custom footer

internal/dis/component/control/static/custom/assets.go

@@ -0,0 +1,22 @@
+package custom
+
+import (
+	"path/filepath"
+
+	"github.com/FAU-CDI/wisski-distillery/internal/dis/component"
+)
+
+// CustomAssetsPath is the path custom assets are stored at
+func (custom *Custom) CustomAssetsPath() string {
+	return filepath.Join(custom.Config.DeployRoot, "core", "assets")
+}
+
+func (custom *Custom) FooterPath() string {
+	return filepath.Join(custom.CustomAssetsPath(), "footer.html")
+}
+
+func (custom *Custom) BackupName() string { return "custom" }
+
+func (custom *Custom) Backup(context component.StagingContext) error {
+	return context.CopyDirectory("", custom.CustomAssetsPath())
+}