how to write an interface in angular

You should check out the interface docs for Typescript. https://www.typescriptlang.org/docs/handbook/2/objects.html

UserId in you example response look like strings.

So for

{
    "courseId": 1,
    "userIds": [
      "46071424",
      "46076456",
    ],
    "endDate": "2022-03-29"
}

your interface could be

interface IModel {
  courseId: number;
  userIds: string[];
  endDate: string;
}

export interface Course {
  courseId: number; 
  userIds: string[];
  endDate: string;
}

TS Object Types

Try this:

interface number{
   courseId: number;
   userIds: any;
   endDate: string;
}

https://www.typescriptlang.org/docs/handbook/interfaces.html

// model 1

interface backendModel{
    courseId : number,
    userIds? : string[],
    endDate?: string
}

// ex :

const model : backendModel = 
    {
        "courseId": 1,
        "userIds": [
          "46071424",
          "46076456",
        ],
        "endDate": "2022-03-29"
    };



// model 2

interface backendModel2{
    courseId : Number,
    userIds? : Number[],
    endDate?: Date
}


const model2 : backendModel2 = 
    {
        "courseId": 1,
        "userIds": [
         Number("46071424"),
         Number( "46076456"),
        ],
        "endDate": new Date("2022-03-29")
    };

// model 3 if all fields are required 

interface backendModel3{
    courseId : number,
    userIds : string[],
    endDate : string
}

Just try http://json2ts.com/. You can convert any JSON to TS from it

Date datatype can be used to get the date in angular since your data in the form of string You can use string too.

export interface AuthResponse{
    
  courseId: number; 
  userIds : string[];
  endDate : Date;
 
}