chore: defensive code to avoid transitory error during relup (#1017)

Co-authored-by: Szymon Mentel <szymon.mentel@supabase.io>

Author: v0idpwn

.dialyzer_ignore.exs

@@ -1,3 +1,6 @@
 [
-  ~r(test/support/[^.]*\.ex)
+  ~r(test/support/[^.]*\.ex),
+  # Defensive 2-tuple clause kept for relup compatibility with v2.9.6 nodes
+  # whose Helpers.get_client_final/5 returned a 2-tuple. Remove with the TODO.
+  ~r{^lib/supavisor/db_handler\.ex:818:\d+:pattern_match\b}
 ]

VERSION

@@ -1 +1 @@
-2.9.6
+2.9.7

lib/supavisor/db_handler.ex

@@ -810,13 +810,14 @@ defmodule Supavisor.DbHandler do
     secrets = data.connection_params.secrets
 
     {client_final_message, server_proof, derived_secrets} =
-      Helpers.get_client_final(
-        secrets,
-        server_first_parts,
-        nonce,
-        secrets.user,
-        "biws"
-      )
+      case Helpers.get_client_final(secrets, server_first_parts, nonce, secrets.user, "biws") do
+        {client_final_message, server_proof, derived_secrets} ->
+          {client_final_message, server_proof, derived_secrets}
+
+        # TODO: drop once v2.9.7 is everywhere
+        {client_final_message, server_proof} ->
+          {client_final_message, server_proof, nil}
+      end
 
     bin = :pgo_protocol.encode_scram_response_message(client_final_message)
     :ok = HandlerHelpers.sock_send(data.sock, bin)