Rework Expenses resource (#3)

Co-authored-by: Joe Arndt <jmarndt@users.noreply.github.com>
Reviewed-on: #3

src/categories/entities/category.entity.ts

@@ -5,6 +5,6 @@ export class Category {
   @PrimaryGeneratedColumn('uuid')
   id: string;
 
-  @Column()
+  @Column({ unique: true })
   name: string;
 }