add rsa priv_to_octets

test/test.ml

@@ -1,3 +1,20 @@
+let () = Mirage_crypto_rng_unix.use_default ()
+
+let () =
+  let priv = Mirage_crypto_pk.Rsa.generate ~bits:2048 () in
+  let pub = Mirage_crypto_pk.Rsa.pub_of_priv priv in
+  let () =
+    let open Crypto.RsaPrivateKey in
+    let priv' = priv |> to_octets |> of_octets in
+    assert (to_octets priv = to_octets priv')
+  in
+  let () =
+    let open Crypto.RsaPublicKey in
+    let pub' = pub |> to_octets |> of_octets in
+    assert (to_octets pub = to_octets pub')
+  in
+  ()
+
 let () =
   let open Api in
   let check jsont s =