Add 'brand' field to MSC2858 response (#9242)

We've decided to add a 'brand' field to help clients decide how to style the
buttons.

Also, fix up the allowed characters for idp_id, while I'm in the area.

1 files changed, 5 insertions, 0 deletions

diff --git a/synapse/handlers/sso.py b/synapse/handlers/sso.py

index afc1341d09..3308b037d2 100644
--- a/synapse/handlers/sso.py
+++ b/synapse/handlers/sso.py
@@ -80,6 +80,11 @@ class SsoIdentityProvider(Protocol):
         """Optional MXC URI for user-facing icon"""
         return None
 
+    @property
+    def idp_brand(self) -> Optional[str]:
+        """Optional branding identifier"""
+        return None
+
     @abc.abstractmethod
     async def handle_redirect_request(
         self,