Is your feature request related to a problem? Please describe.
In the upcoming serverless runtime for Jolie (currently located at lucat1/jfn) I'd like to run "functions" (aka microservices with only one method) in either concurrent or single execution mode. Single mode is meant for functions which get called rarely; if we have a high load on a function though, it is wise to promote it to a service until the load decreases.

Describe the solution you'd like
I'd be interested in being able to use a service parameter to define the execution type. That would allow me to specify it as a parameter when dynamically embedding.

Describe alternatives you've considered
The only alternative I can think of currently is doing s/execution: \w+/execution: WHATIWANT/, which is not reliable and could lead to replacements where they shouldn't happen. A more polished but still clunky alternative is to edit the AST, but I'm not certain I can do this in Jolie, so I'd have to bridge some Java code.