happa release v1.57.8

What’s Changed

• Support selecting an empty option for JSON schema form select boxes by @gusevda in https://github.com/giantswarm/happa/pull/4134
• Preprocess default values for the JSON schema form by @gusevda in https://github.com/giantswarm/happa/pull/4132
• Internal changes towards supporting cluster creation based on app bundles by @kuosandys in https://github.com/giantswarm/happa/pull/4144

Full Changelog: https://github.com/giantswarm/happa/compare/v1.57.7...v1.57.8