[Feature Request] @delegate based on multiple fields

[hechang27-sprt]

Quite annoying to have to de-normalize a combined key just so that it can be used for @@delegate:

model Base {
  appKey String
  collectionKey String
  // @@delegate(appKey, collectionKey) -- Doesn't work
  combinedKey String @computed // generates just fine but produces error at runtime 
}

not to mention that that de-normalized column can't even use a @computed and has to be maintained in code.