add upload api and cdn to serve uploaded images

[guilbep]

We should have a way of uploading images and serving them like for unhcr

Duplicate the following services:

• upload-fast-api

• the s3_server

• Create a new s3 bucket specifically for this project (alice-ethz-arema)

[ymarcon]

S3 access keys and secrets are in the admin's keystore: s3 arema read / s3 arema write.

In the .env

# used by nginx s3 service and fast api boto api
S3_ENDPOINT_HOSTNAME=s3.epfl.ch
S3_ENDPOINT_PROTOCOL=https://
S3_ACCESS_KEY_ID=xxxxxxxx
S3_SECRET_ACCESS_KEY=xxxxxxxxx
S3_REGION=EU
S3_Bucket=10208-3dc6ab3b82a468a070599cbdb7c049c0
# for instance if S3_Key is foo/bar/ ; the url will start with: /s3/foo/bar/
S3_Key=arema