Polymorphic Embeddables in combination with embedded properties

[dehrhard]

Describe the bug
I have an issue when using Polymorphic Embeddables in combination with nested embedded properties. When two Polymorphs have a property with the same name their type is conflicting and ending mixed up. I think I traced the issue to this spot in

mikro-orm/packages/core/src/metadata/MetadataDiscovery.ts

Line 661 in 473795c

polymorphs.forEach(meta => {

polymorphs.forEach(meta => {
  Object.values(meta.properties).forEach(prop => properties[prop.name] = prop);
  processExtensions(meta);
});

The properties Object receives the properties from both polymorhps. If multiple polymorphs have the same property name, the latter overwrites the former.

Example
Consider the shortened example from the Docs

export enum AnimalType {
  CAT,
  DOG,
}

@Embeddable()
export class CatFood {

  @Property()
  mice = 2;
}

@Embeddable()
export class DogFood {

  @Property()
  cats = 10;
}

@Embeddable({ abstract: true, discriminatorColumn: 'type' })
export abstract class Animal {
  @Enum()
  type!: AnimalType;

  @Property()
  name!: string;
}

@Embeddable({ discriminatorValue: AnimalType.CAT })
export class Cat extends Animal {

  @Property()
  canMeow? = true;

  @Embedded()
  food: CatFood;
}

@Embeddable({ discriminatorValue: AnimalType.DOG })
export class Dog extends Animal {

  @Property()
  canBark? = true;

  @Embedded()
  food: DogFood;
}

@Entity()
export class Owner {
  @PrimaryKey()
  id!: number;

  @Property()
  name!: string;

  @Embedded()
  pet!: Cat | Dog;
}

In this case the food property of class Cat/Dog is ambiguos and depending on which polymorph is processed first, food might receive type Dogfood for Polymorph Cat or receive type Catfood for Polymorph Dog

Expected behavior
Depeding on the used polymorph, the property should receive the associated type

Versions

Dependency	Version
node	16
typescript	4.6.2
mikro-orm	5.0.4
@mikro-orm/postgresql	5.0.4