[server] fix private GitHub avatars

[filiptronicek]

Description

A recent GitHub change changed the way of accessing a user's avatar. Potentially as an anti-bot/spam measure, GitHub now issues JWT-signed URLs for avatars on both https://github.com and as part of their API responses to some users, making it impossible for us to continue storing them like we do now - i.e. without any refreshes ever. Additionally, these JWT signatures inflate the URL length, preventing it from fitting into our DB's avatarUrl column.

Let's take a look at the new URL structure:

https://private-avatars.githubusercontent.com/u/37021919?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJnaXRodWIuY29tIiwiYXVkIjoicmF3LmdpdGh1YnVzZXJjb250ZW50LmNvbSIsImtleSI6ImtleTEiLCJleHAiOjE3MzQ0MjYwMDAsIm5iZiI6MTczNDQyNDgwMCwicGF0aCI6Ii91LzM3MDIxOTE5In0.zOrR2kgZWVvZqcVgoUwADtQqQmZ6Yh9Tie1CQPi7ADY&s=200&v=4

Here, we can see the jwt query param being used to authorize the request. If it's omitted, invalid, or when the underlying JWT expires, we get a 404.

The old avatar URLs seem to still work as before, but don't get issued anymore to the users in this cohort.

https://avatars.githubusercontent.com/u/37021919?v=4

What this PR does is that it simply rewrites the private-avatars.githubusercontent.com URL into a avatars.githubusercontent.com if it encounters it.

Related Issue(s)

Fixes CLC-1050

How to test

Try logging in into the preview environment, that's all.

https://ft-gh-public-avatars.preview.gitpod-dev.com/workspaces

/hold

[filiptronicek]

I raised a discussion about this in the GitHub community forum: https://github.com/orgs/community/discussions/147297