List.ts

import { Entity, Column, ManyToOne, OneToMany } from 'typeorm';
import { BaseEntity } from './BaseEntity';
import { Project } from './Project';
import { Task } from './Task';

@Entity()
export class List extends BaseEntity {
    @Column('varchar') name!: string;

    @ManyToOne(type => Project, project => project.lists)
    project!: Project;

    @OneToMany(type => Task, task => task.list)
    tasks!: Task[];
}

Task.ts

import { Entity, Column, ManyToOne, OneToMany } from 'typeorm';
import { BaseEntity } from './BaseEntity';
import { List } from './List';
import { TaskMutation } from './TaskMutation';

@Entity()
export class Task extends BaseEntity {
    @Column('varchar') title!: string;

    @Column('varchar', { nullable: true })
    assignee!: string;

    @ManyToOne(type => List, list => list.tasks)
    list!: List;

    @OneToMany(type => TaskMutation, mutation => mutation.task)
    mutations!: TaskMutation[];
}