[REQ][typescript-nestjs] Accept async function for fetching access token

Is your feature request related to a problem? Please describe.

Most access tokens are fetched with async/network requests which the current ConfigurationParameters doesn't support.

export interface ConfigurationParameters {
    apiKeys?: {[ key: string ]: string};
    username?: string;
    password?: string;
    accessToken?: string | (() => string);
    basePath?: string;
    withCredentials?: boolean;
}

Describe the solution you'd like

ConfigurationParameters.accessToken should start supporting the following signature

export interface ConfigurationParameters {
    ...
    accessToken?: string | Promise<string> | (() => string) | (() => Promise<string>);
    ...
}

Describe alternatives you've considered

None

Additional context

This issue is similar to https://github.com/OpenAPITools/openapi-generator/issues/7105

Start by locating the TypeScript NestJS ConfigurationParameters interface and the generated client code that consumes accessToken. Check how the current string and synchronous function forms are handled, then run the related generated-client tests if present. Done means accepting string, Promise, and synchronous or asynchronous functions for accessToken.