Improve performance of user avatar loading

Currently due to the non-working caching of avatars + assets I took a look backstage on what we are actually doing when we are loading a simple public user avatar. Found during the investigation of !18345 (merged).

• Check feature flags (which might be even a global problem)
• Load Identity, User, UserConfiguration

Most probably have we exactly the same problem also for other assets.

Why can't we especially in the case of the user avatar not just load/pipe the asset and if it doesn't exist end with 404? As the Frontend in reality should already check if there is an avatar or not.

Jaeger trace