Cache response from /api/user_photo

[anders-kiaer]

Every time the user visits webviz application + open the ensemble dialog box, there are multiple requests towards /api/user_photo, one for each unique user in the case list (which takes some time to complete). Each user photo can be several MB in size also.

webviz/backend/src/backend/primary/routers/graph/router.py

Line 17 in dd075c1

@router.get("/user_photo/")

We can probably cache the response from this endpoint quite aggresively (order of days/couple of weeks?). Having a stale/outdated user profile for some time is no big issue (it also very rarely change - many years on average between user photo changes), compared to the upside of having faster rendering in client + fewer API requests to be handled by primary backend.