Import image asset uploaded through the API if it already is in the data store but not in the database

[Toastbrot236]

Uploading an image asset using the API which already is in the data store but not the database will result in an InternalServerError response, which for example prevents users from setting their profile picture to an image which happens to be in a state like that. It might be better if we instead try importing that asset and then working with the resulting GameAsset, considering the endpoint method already uses an AssetImporter parameter.