Description
The /{keyId} parameter has been removed in Matrix v1.6. This version of the specification also included another change that mandates a 404 response for requests to unsupported endpoints:
If a request for an unsupported (or unknown) endpoint is received then the server must respond with a 404 M_UNRECOGNIZED error.
However, Synapse appears to still respond to requests with /{keyId} as if the path component was missing. See e.g. https://matrix-federation.matrix.org/_matrix/key/v2/server/foo which returns the same 200 response as https://matrix-federation.matrix.org/_matrix/key/v2/server rather than a 404.
I assume this might actually be intentional because until late 2022 Synapse itself specified the parameter on outgoing requests. However, given that this isn't part of the spec anymore I'm curious what the migration path is here, if any?
For context: I'm poking at this with my gematik hat on as we're trying to expose and prevent compatibility problems within the gematik ecosystem. The latter is currently on Matrix v1.3 but once we update our specification we'll also have v1.10 implementations in the same federation.