A server entry's OAuth client ID already has a meaning while OAuth is
off globally: it is the registered client that password and TOTP logins
use with Stalwart's require_client_registration. The PR made every such
entry offer OAuth on its own, so existing installs would suddenly run
discovery and show SSO buttons on the login page, and multi-IdP setups
would get one extra button per server.
A server now gets its own button only with both a client ID and a button
label, which no existing config has. The rule lives in `offersOwnOAuth`
with a test. Also:
- the OAuth-only login form uses the selected server's label
- the public config validator checks `buttonLabel` is a string
- the admin hint and `.env.example` say the label enables the button
A server entry that names its own OAuth client now offers the OAuth
button even while OAuth is off globally, so a Gmail bridge can sign in
with Google next to a server that uses passwords. The entry can also
name the button ("Sign in with Google"); the generic SSO label stays
the default.
Linus Rath
lucamzanon