Remove unstable support for MSC2732

This MSC was accepted in 2022. We shouldn't need to continue supporting the unstable endpoint.

Removing this saves us from needing to support it in the pydantic model (which is much easier in pydantic v2 than v1).

Author: anoadragon453

synapse/rest/client/sync.py

@@ -363,9 +363,6 @@ async def encode_response(
 
         # https://github.com/matrix-org/matrix-doc/blob/54255851f642f84a4f1aaf7bc063eebe3d76752b/proposals/2732-olm-fallback-keys.md
         # states that this field should always be included, as long as the server supports the feature.
-        response["org.matrix.msc2732.device_unused_fallback_key_types"] = (
-            sync_result.device_unused_fallback_key_types
-        )
         response["device_unused_fallback_key_types"] = (
             sync_result.device_unused_fallback_key_types
         )

tests/handlers/test_e2e_keys.py

@@ -410,7 +410,6 @@ def test_fallback_key(self) -> None:
         device_id = "xyz"
         fallback_key = {"alg1:k1": "fallback_key1"}
         fallback_key2 = {"alg1:k2": "fallback_key2"}
-        fallback_key3 = {"alg1:k2": "fallback_key3"}
         otk = {"alg1:k2": "key2"}
 
         # we shouldn't have any unused fallback keys yet
@@ -531,28 +530,6 @@ def test_fallback_key(self) -> None:
             {"failures": {}, "one_time_keys": {local_user: {device_id: fallback_key2}}},
         )
 
-        # using the unstable prefix should also set the fallback key
-        self.get_success(
-            self.handler.upload_keys_for_user(
-                local_user,
-                device_id,
-                {"org.matrix.msc2732.fallback_keys": fallback_key3},
-            )
-        )
-
-        claim_res = self.get_success(
-            self.handler.claim_one_time_keys(
-                {local_user: {device_id: {"alg1": 1}}},
-                self.requester,
-                timeout=None,
-                always_include_fallback_keys=False,
-            )
-        )
-        self.assertEqual(
-            claim_res,
-            {"failures": {}, "one_time_keys": {local_user: {device_id: fallback_key3}}},
-        )
-
     def test_fallback_key_bulk(self) -> None:
         """Like test_fallback_key, but claims multiple keys in one handler call."""
         alice = f"@alice:{self.hs.hostname}"