[NDD-159]: Category 객체, 리포지토리 구현 (1h / 1h) (#43)

* feat: 카테고리 객체 생성'

* feat: Category를 DB에 저장하고, 조회하는 Repository구현

* fix: dev rebase를 위해 conflict나는 app.module 임시 롤백

BE/src/category/category.module.ts

@@ -0,0 +1,7 @@
+import { Module } from '@nestjs/common';
+import { CategoryRepository } from './repository/category.repository';
+
+@Module({
+  providers: [CategoryRepository],
+})
+export class CategoryModule {}

BE/src/category/entity/category.ts

@@ -0,0 +1,32 @@
+import { Column, Entity, JoinTable, ManyToMany, ManyToOne } from 'typeorm';
+import { DefaultEntity } from '../../app.entity';
+import { Member } from '../../member/entity/member';
+import { JoinColumn } from 'typeorm/browser';
+import { Question } from '../../question/entity/question';
+
+@Entity({ name: 'Category' })
+export class Category extends DefaultEntity {
+  @Column()
+  name: string;
+
+  @ManyToOne(() => Member, { nullable: true, onDelete: 'CASCADE' })
+  @JoinColumn({ name: 'member' })
+  member: Member;
+
+  @ManyToMany(() => Question)
+  @JoinTable({ name: 'CategoryQuestion' })
+  questions: Question[];
+
+  constructor(name: string) {
+    super(undefined, new Date());
+    this.name = name;
+  }
+
+  static copyCategory(category: Category) {
+    return new Category(category.name);
+  }
+
+  getName() {
+    return this.name;
+  }
+}

BE/src/category/repository/category.repository.ts

@@ -0,0 +1,24 @@
+import { Injectable } from '@nestjs/common';
+import { InjectRepository } from '@nestjs/typeorm';
+import { Category } from '../entity/category';
+import { Repository } from 'typeorm';
+
+@Injectable()
+export class CategoryRepository {
+  constructor(
+    @InjectRepository(Category) private repository: Repository<Category>,
+  ) {}
+
+  async save(category: Category) {
+    await this.repository.save(category);
+  }
+
+  async findAllByMemberId(memberId: number) {
+    const option = memberId === null ? null : { id: memberId };
+    return await this.repository.findBy({ member: option });
+  }
+
+  async remove(category: Category) {
+    await this.repository.remove(category);
+  }
+}