Generated Client mustBeSet check fails for Set-Cookie

[tuckers-tech]

Hey all! Loving Encore TS! I ran into an issue with the generated client this evening.

I have an AuthResponse defined in the following way:

export interface AuthResponse {
  cookies: Header<'Set-Cookie'>
  user: User
}

When generated, it outputs the following:

public async login(params: LoginParams): Promise<AuthResponse> {
    // Now make the actual call to the API
    const resp = await this.baseClient.callAPI("POST", `/auth/login`, JSON.stringify(params))

    //Populate the return object from the JSON body and received headers
    const rtn = await resp.json() as AuthResponse
    rtn.cookies = mustBeSet("Header `set-cookie`", resp.headers.get("set-cookie"))
    return rtn
}

The mustBeSet call for set-cookie is failing because Set-Cookie is a forbidden response header. Encore itself is setting that header correctly, but the generated client should not expect to be able to access the Set-Cookie header.