Support for authenticated media

[kfiven]

After the landing of matrix-org/matrix-spec-proposals#3916 the profile picture of mxid does not load.

Example: https://matrix.to/#/@ukiradante:matrix.org

[t3chguy]

This will be tricky given that matrix.to doesn't actually have any credentials to authenticate with, it relies on unauthenticated APIs exclusively.

[ShadowRZ]

Giving credentials doesn't seems correct to me, as a credential would only apply to a single homeserver while matrix.to supports using other servers to get the preview.

Also IMO using credentials in matrix.to would complicate the implmentation of matrix.to, as to protect the credential, it should use a server side request to the authenticated endpoints, thus requiring the matrix.to to also have a private endpoint to fetch media itself, very similar to what some bridges should do.

[ara4n]

at the least, we should have the missing profile fail gracefully rather than just looking like this:

[arnowelzel]

But how does it work then with other servers? For example, here the avatar can be loaded without any issue (at least when I checked it):

https://matrix.to/#/@jaywink:federator.dev
https://matrix.to/#/@bubu:bubu1.eu
https://matrix.to/#/@peter.scholtens:matrix4me.nl

Is there any setting in the server to allow avatar downloading without credentials?

Otherwise I would also suggest using a placeholder if the image can not be loaded, similar to the situation when a user does not have an avatar at all:

[nOw-Ay]

@ara4n @arnowelzel, the PR I’m proposing makes image loading fail gracefully by falling back to the placeholder instead of showing nothing. I think this is quite important since many people use matrix.to, and the current behavior gives an “unfinished” impression that isn’t really warranted.

at the least, we should have the missing profile fail gracefully rather than just looking like this:

[xelayz]

Thank you @nOw-Ay

A placeholder would be great.