v0.12.8

What's Changed

• Move metrics ets creation to stalker by @mat-hek in #589
• Refactor code related to crash groups and linking mechanism by @FelonEkonom in #574
• Fix specs for default pipeline functions by @FelonEkonom in #585
• Fix stream format error message, fix race condition in handling child pad removed by @FelonEkonom in #591

Full Changelog: v0.12.7...v0.12.8