Add Request body Schema in loopback4

I'm new with loopback 4 and I really have difficulty with the documentation that is some time not up to date. I succeed to add an authentification system and a route to log in to the users. My problem is on the "/explorer" URL, I don't know how can I add example value on the request body schema of a custom route.

There is my route:

@post('/users/login', {
    responses: {
      '200': {
        description: 'Token',
        content: {
          'application/json': {
            schema: {
              type: 'object',
              properties: {
                token: {
                  type: 'string'
                }
              }
            }
          }
        }
      }
    }
  })
  async login(
    @requestBody() credentials: Credentials,
  ): Promise<{token: string}> {
    // make sure user exist,password should be valid
    const user = await this.userService.verifyCredentials(credentials);
    // console.log(user);
    const userProfile = await this.userService.convertToUserProfile(user);
    // console.log(userProfile);

    const token = await this.jwtService.generateToken(userProfile);
    return Promise.resolve({token: token})
  }

And I wish to add:

{
   "username": "string",
   "password": "string"
}

Here:

I suppose that there is a simple way to do it but I really can't find anything about it.

Solution

FYI: The loopback4 uses the route Decorator, which provides OpenAPI specification to describe the endpoint. There is en-detailed about OpenAPI decorator in loopbac4 here.
Now to solve the above issue. lets create:

Schema for User Login i.e {"username":string, "password":string} in the schema definition you can also add the validation rules.

const  UserLoginSchema = {
type: 'object',
required: ['email', 'password'],
properties: {
  username: {
    type: 'string',
  },
  password: {
    type: 'string',
  },
},
}; ```

Now lets quickly create your RequestBody c'tor for login. Remember as per OpenApi Specification the request body would contain description, required and content.

 export const UserLoginRequestBody = {
      description: 'Required input for login',
      required: true,
      content: {
        'application/json': {schema: UserLoginSchema},
      },
    };

Now you are ready to use your request body.

  async login(
    @requestBody(UserLoginRequestBody) credentials: Credentials,
  ): Promise<{token: string}> {
..restCode

Thats get you done.