MSC2499: Fixes for Well-known URIs

proposals/2499-client-well-known-fixes.md

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+# MSC2499: Fixes for Well-Known URIs
+
+Several minor issues and inconsistencies have come up with the well-known URIs used for
+discovering clients and servers. This proposal intends to fix these issues.
+
+## Proposal
+
+The following changes should be made to the spec:
+
+1. The spec does not mention that redirects should be followed for `/.well-known/matrix/client`
+and does not clearly specify what type of redirects should be followed for `/.well-known/matrix/server`.
+To fix this, the spec should be changed to state that when a well-known URI is requested,
+the client or server should follow HTTP 301, 302, 303, 307, and 308 redirects up to 30 times.
+
+1. Currently the spec does not mention which Content-Type should be used for the response to
+`/.well-known/matrix/client`. The Client-Server spec should be changed to state the Content-Type
+SHOULD be `application/json` however it should be assumed to be JSON regardless of Content-Type.
+This is consistent with the Server-Server API.
+
+1. Step 3f in the Client-Server well-known flow should be changed to use the modern
+`/_matrix/identity/versions` API to validate the identity server rather than the deprecated
+`/_matrix/identity/api/v1`.
+
+1. Mark the `/_matrix/identity/v2` status check API as deprecated. `/_matrix/identity/versions`
+is the suggested replacement.
+
+1. The maximum size of size of the well-known file is 51200 bytes. A client or server
+requesting a well-known file MUST abort and FAIL_PROMPT if the response exceeds 51200 bytes.