How to create a partial payload that adheres to an interface?

I have the following code where I have 2 interfaces that have shared data. Since the real life object is so big I don't want to repeat myself to avoid errors and keep the code solid. However I cannot figure out how to implement this in a way that would make it compatible. I keep getting an error like there are fields that are missing.

export interface UserDoc {
   user: string;
   consent: boolean;
   programs: string;
   data: string;
}
 
export interface AdminDoc extends Omit<UserDoc, 'programs' | 'data'> {
user: string;
consent: boolean;
src: string;
}

// Shared fields
export const createSharedPayload = (): Partial<UserDoc | AdminDoc> => {
  return {
     user: '',
     consent: false,
}

const userPayload: UserDoc = {
     ...createSharedPayload(),
   programs:[],
   data: []
}

const adminPayload: AdminDoc = {
     ...createSharedPayload(), 
     src: 'some string'
}

How to make this bundle work together?

The standard OOP approach would be to abstract away the shared fields in a common super-interface:

interface Doc {
   user: string;
   consent: boolean;
}

export interface UserDoc extends Doc {
   programs: string[];
   data: string[];
}
 
export interface AdminDoc extends Doc {
  src: string;
}

export const createSharedPayload = (): Doc => {
  return {
     user: '',
     consent: false
  }
};

const userPayload: UserDoc = {
     ...createSharedPayload(),
   programs:[],
   data: []
};

const adminPayload: AdminDoc = {
     ...createSharedPayload(), 
     src: 'some string'
}

Playground link

Instead of using Omit to remove some properties, you should instead create a base class BaseDoc to define the common ones.

export interface BaseDoc  {
  user: string;
  consent: boolean;
}

export interface AdminDoc extends BaseDoc {
  src: string;
}

export interface UserDoc extends BaseDoc {
  programs: string;
  data: string
}

export const createSharedPayload = (): Partial<BaseDoc> => {
  return {
    user: '',
    consent: false
  }
}

const userPayload: UserDoc = {
  ...createSharedPayload(),
  programs: '',
  data: ''
}

const adminPayload: AdminDoc = {
  ...createSharedPayload(),
  src: ''
}