Add additional checks in frontend when creating a function

[bisgaard-itis]

Long Story Short
I tried to create and run a function which has no computational studies. Running the function via the api-server (which is what the metamodeling service does under the hood) fails with 422.

Expected Behavior

• I expect to get a 422 in the api-server, but with a more descriptive error message. I believe the 422 is propagated from the director-v2. So it should be converted into a more meaningful message.
• I expect the frontend already to check that my study has at least one computational service and no dynamic services before allowing me to create a function.