@SubclassMapping selecting implementation class based on source field value

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### Use case

It is common practice saving multiple sub-classes into one database tables. E.g.:
I have a db entity Contact with type field value
```kotlin
@Entity
@Table(name = CONTACTS_TABLE)
open class ContactEntity {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id: Long = 0

@Column(name = CONTACT_TYPE_COLUMN, nullable = false)
var type: ContactType = ContactType.BUSINESS
}
```
My domain model Contact is abstract and can have two implementations: BusinessContact and NaturalPersonContact:
```kotlin
sealed interface Contact {
val id: Long
}

data class BusinessContact(
override val id: Long,
val businessName: String,
) : Contact

data class NaturalPersonContact(
override val id: Long,
val firstName: String,
val lastName: String,
) : Contact
```
Trying to define a Mapper with `@SubclassMapping` has no option to add logic to it based on type property:
```kotlin
@SubclassMapping(target = BusinessContact::class, source = ContactEntity::class)
@SubclassMapping(target = NaturalPersonContact::class, source = ContactEntity::class)
fun entityToDomainModel(entity: ContactEntity): Contact
```

### Generated Code

_No response_

### Possible workarounds

None known

### MapStruct Version

implementation("org.mapstruct:mapstruct:1.5.5.Final")

Start by examining how @SubclassMapping is processed for the ContactEntity-to-Contact mapper described in the issue, including the MapStruct 1.5.5.Final behavior. Done should support selecting BusinessContact or NaturalPersonContact from the source type property and include coverage for that generated mapping.

Written by the indexing model from the issue text.