Support staging workflow

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**Tell us about your request**
As a Developer
I would like to deploy my application (from source code) within multiple stages (like dev and prod) without executing the build multiple times.

**Describe alternatives you've considered**
The current alternative is to create two AppRunner services with different branches, still the build is executed multiple times.

**Additional context**
A support for individual workflows would be nice incl:
- manual trigger deployment per stage
- run some test against deployed service, before next deployment is triggered