approle: convert Callbacks to Operations (#11893)

* approle: convert Callbacks to Operations

The usage of oldstyle "Callbacks" is causing the `cannot write to readonly
storage` error message when `login` is attempted against a performance standby.

Use the newstyle "Operations" and additionally set the Forward
parameters to forward the request to the Active vault node.

* add changelog

* do not forward for alias lookahead operation

* remove forward fields and remove changelog

- Because this request is an UpdateOperation, it should have automatically been
routed to the primary/active by the router before it reaches the backend.
- changelog should not be needed as this change is only a refactor with
no user-facing behavior changes.

builtin/credential/approle/path_login.go

@@ -26,9 +26,13 @@ func pathLogin(b *backend) *framework.Path {
 				Description: "SecretID belong to the App role",
 			},
 		},
-		Callbacks: map[logical.Operation]framework.OperationFunc{
-			logical.UpdateOperation:         b.pathLoginUpdate,
-			logical.AliasLookaheadOperation: b.pathLoginUpdateAliasLookahead,
+		Operations: map[logical.Operation]framework.OperationHandler{
+			logical.UpdateOperation: &framework.PathOperation{
+				Callback: b.pathLoginUpdate,
+			},
+			logical.AliasLookaheadOperation: &framework.PathOperation{
+				Callback: b.pathLoginUpdateAliasLookahead,
+			},
 		},
 		HelpSynopsis:    pathLoginHelpSys,
 		HelpDescription: pathLoginHelpDesc,