GraphQL display problem Error: Body must be a string. Received: undefined

[jschoba]

Bug description

GraphQL API is not displayed in the Self-hosted developer portal, we got a loading sign which never stops.

Reproduction steps

1. Import Synthetic GraphQL API with sample schema
2. Open Graph QL API in developer portal
3. Nothing is displayed on the page

Expected behavior

A javascript exception is displayed:
Error: Body must be a string. Received: undefined.
at devAssert (webpack://apim-developer-portal/./node_modules/graphql/jsutils/devAssert.mjs?:9:11)
at new Source (webpack://apim-developer-portal/./node_modules/graphql/language/source.mjs?:33:99)
at new Parser (webpack://apim-developer-portal/./node_modules/graphql/language/parser.mjs?:84:94)
at parse (webpack://apim-developer-portal/./node_modules/graphql/language/parser.mjs?:31:16)
at Module.buildSchema (webpack://apim-developer-portal/./node_modules/graphql/utilities/buildASTSchema.mjs?:101:77)
at GraphDocService.eval (webpack://apim-developer-portal/./src/components/operations/operation-details/ko/runtime/graphql-documentation/graphql-doc-service.ts?:66:40)
at Generator.next ()
at fulfilled (webpack://apim-developer-portal/./src/components/operations/operation-details/ko/runtime/graphql-documentation/graphql-doc-service.ts?:5:58)

Is self-hosted portal?

Yes

Release tag or commit SHA (if using self-hosted version)

release tag2.27

Environment

azure static web app

Additional context

Example Schema that we used:

type User {
id: ID!
username: String!
email: String!
createdAt: String!
reservations: [Reservation!]!
}

type Reservation {
id: ID!
userId: ID!
startDate: String!
endDate: String!
status: String!
createdAt: String!
user: User!
}

type Query {
users: [User!]!
user(id: ID!): User
reservations: [Reservation!]!
reservation(id: ID!): Reservation
}

type Mutation {
createUser(username: String!, email: String!): User!
createReservation(userId: ID!, startDate: String!, endDate: String!, status: String!): Reservation!
updateReservation(id: ID!, startDate: String, endDate: String, status: String): Reservation!
deleteReservation(id: ID!): Boolean!
}