Missing type parameter on /thumbnail endpoint

[clokep]

Link to problem area: https://spec.matrix.org/v1.5/client-server-api/#get_matrixmediav3thumbnailservernamemediaid

Issue
Synapse supports a type parameter (which defaults to image/png if not provided), this is not in the spec, but has existed since this endpoint has.

matrix-media-repo does not seem to support this.

Dendrite does not seem to support this either, although declares it uses a similar algorithm to Synapse to find thumbnails.

Expected behaviour
Add the type parameter, as documented above.

As an aside, @Half-Shot rightly pointed out that this is what Accept headers are for?

[turt2live]

This is indeed what Accept headers are for. Given this feature has not proved useful in practice, it feels best described as a Synapse Feature rather than as Spec Omission - closing accordingly (an MSC can be opened to add it).

[clokep]

Thanks for the clarification. I've filed matrix-org/synapse#14913