Scalar Date is not working

I defined the scalar date according to the documentation. But if I try to create a new entry with a date, I get a type mismatch error from rust when writing to he database.

I just compiled the schema.graphql and initialized the database with the sql script.

When I change the column type in the database directly to type date, the queries and mutations work fine.

See Type Vertrag and CreateVertrag. These are parts of the schema file.

directive @bb_primaryKey on FIELD_DEFINITION
directive @bb_resolver on FIELD_DEFINITION

scalar DueDate @bb_scalar(_type: “Date”)

type Vertrag {
id: ID!
name: String!
hik: Int!
description: String
gueltigvon: DueDate!
gueltigbis: DueDate!

name: String!,
description: String,
hik: Int!
gueltigvon: DueDate!,
gueltigbis: DueDate!
): Task
_type: INSERT,
_object: Vertrag,
_fields: {
name: “$name”,
description: “$description”,
hik: “$hik”,
gueltigvon: “$gueltigvon”,
gueltigbis: “$gueltigbis”)