Implement callback for update PublicAsset when remove IdentityId

[vttranlina]

Why?

When I remove an identity, other identity ids shall be removed in the background
original: #1050 (comment)

How

• Requirement: CustomIdentityDAO support callback mechanism when delete james-project#5198
• Create a class PublicAssetIdentityCallback extends IdentityCallback,
  The code looks like this:

class PublicAssetIdentityCallback @Inject()(publicAssetRepository: PublicAssetRepository) extends IdentityCallback {

  override def identityRemoved(username: Username, identityId: IdentityId): Publisher[Void] = {
    // get all public assets for the user
    // then filter the public assets that have the identityId
    // then remove the identityId from the public asset
    SFlux(publicAssetRepository.list(username))
      .flatMap(publicAsset => {
        val updatedIdentityIds: Seq[IdentityId] = publicAsset.identityIds.filterNot(_ == identityId)
        publicAssetRepository.update(username, publicAsset.id, updatedIdentityIds.toSet)
      })
      .`then`()
  }
}

Dod

• Unit test
• jmap integration test