✨ functions: support enum argument types

[rsteube]

What are you trying to do?

• Provide a way to define possible argument values of functions (e.g. [male, female] for gender).

Why is this important to you?

shell completion

How are you currently working around this?

No response

[helderco]

High level design for the schema required for this:

• feat: add scalar kind #7158 (comment)

To support defining new enums via the API it’s similar to ObjectTypeDef, where the fields are just a list of values and their descriptions:

type EnumTypeDef {
  name: String!
  description: String!
  values: [EnumValueTypeDef!]!
}

type EnumValueTypeDef {
  name: String!
  description: String!
}

type TypeDef {
  """
  If kind is ENUM_KIND, the enum-specific type definition.
  If kind is not ENUM_KIND, this will be null.
  """
  asEnum: EnumTypeDef
    
  """
  Returns a TypeDef of kind Enum with the provided name.
  
  Note that an enum's values may be omitted if the intent is only to refer to an enum.
  This is how functions are able to return their own, or any other circular reference.
  """
  withEnum(name: String!, description: String = ""): TypeDef!

  """
  Adds a static value for an Enum TypeDef, failing if the type is not an enum.
  """
  withValue(name: String!, description: String = ""): TypeDef!
}

enum TypeDefKind {
  """
  A GraphQL enum type and its values.
  
  Always paired with an EnumTypeDef.
  """
  ENUM_KIND
}