Add optional rate limiting for oauth entrypoint

rc_auth/Cargo.toml

@@ -18,6 +18,7 @@ futures.workspace = true
 clap.workspace = true
 oj_rc_core = { version = "*", path = "../rc_core" }
 openidconnect.workspace = true
+chrono.workspace = true
 urlencoding.workspace = true
 libfj.workspace = true
 git-version.workspace = true