[BUG] [typescript-angular] TypeScript compilers errors for generated code if configuration "exactOptionalPropertyTypes" is enabled

[jase88]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?

Description

Every generated openapi code from typescript-angular fails, if the tsconfig.json compiler option exactOptionalPropertyTypes is set to true.

The reason is that in the constructor of configuration.ts a potential undefined value is assigned, although the corresponding property is only optional.
e.g.

export interface ConfigurationParameters {
    //...
    username?: string;
    //...
}

export class Configuration {
    // ...
    username?: string;
    // ...
    constructor(configurationParameters: ConfigurationParameters = {}) {
        // ...
        this.username = configurationParameters.username;
        // ...
    }
}

openapi-generator version

v7.10.0
probably no regression

OpenAPI declaration file content or url

this error occurs on every API definition. Steps below described to get the error within the given angular examples in the repo

Steps to reproduce

• modify samples/client/petstore/typescript-angular-v19/builds/default/tsconfig.json and add

    "strictNullChecks": true,
    "exactOptionalPropertyTypes": true,

to the compilerOptions

• run ./bin/ts-typecheck-all.sh

Related issues/PRs

#14793