feat!: remove legacy REST (backport #9594)

CHANGELOG.md

@@ -45,6 +45,15 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 * (deps) [\#9956](https://github.com/cosmos/cosmos-sdk/pull/9956) Bump Tendermint to [v0.34.12](https://github.com/tendermint/tendermint/releases/tag/v0.34.12).
 
+### API Breaking Changes
+
+* [\#9594](https://github.com/cosmos/cosmos-sdk/pull/9594) `RESTHandlerFn` argument is removed from the `gov/NewProposalHandler`.
+* [\#9594](https://github.com/cosmos/cosmos-sdk/pull/9594) `types/rest` package moved to `testutil/rest`.
+
+### Client Breaking Changes
+
+* [\#9594](https://github.com/cosmos/cosmos-sdk/pull/9594) Remove legacy REST API. Please see the [REST Endpoints Migration guide](https://docs.cosmos.network/master/migrations/rest.html) to migrate to the new REST endpoints.
+
 ### Deprecated
 
 * (x/upgrade) [\#9906](https://github.com/cosmos/cosmos-sdk/pull/9906) Deprecate `UpgradeConsensusState` gRPC query since this functionality is only used for IBC, which now has its own [IBC replacement](https://github.com/cosmos/ibc-go/blob/2c880a22e9f9cc75f62b527ca94aa75ce1106001/proto/ibc/core/client/v1/query.proto#L54)

client/docs/config.json

@@ -1,17 +1,11 @@
 {
   "swagger": "2.0",
   "info": {
-    "title": "Cosmos SDK - Legacy REST and gRPC Gateway docs",
-    "description": "A REST interface for state queries, legacy transactions",
+    "title": "Cosmos SDK - gRPC Gateway docs",
+    "description": "A REST interface for state queries",
     "version": "1.0.0"
   },
   "apis": [
-    {
-      "url": "./client/docs/swagger_legacy.yaml",
-      "dereference": {
-        "circular": "ignore"
-      }
-    },
     {
       "url": "./tmp-swagger-gen/cosmos/auth/v1beta1/query.swagger.json",
       "operationIds": {