blueprint: add filesystem minsize function

internal/blueprint/customizations.go

@@ -200,3 +200,19 @@ func (c *Customizations) GetFilesystems() []FilesystemCustomization {
 	}
 	return c.Filesystem
 }
+
+func (c *Customizations) GetFilesystemsMinSize() uint64 {
+	if c == nil {
+		return 0
+	}
+	agg := 0
+	for _, m := range c.Filesystem {
+		agg += m.MinSize
+	}
+	// This ensures that file system customization `size` is a multiple of
+	// sector size (512)
+	if agg%512 != 0 {
+		agg = (agg/512 + 1) * 512
+	}
+	return uint64(agg)
+}