Improve login.supported_modes

Fix schema

apiserver/apimodels/login.py

@@ -1,4 +1,4 @@
-from jsonmodels.fields import StringField, BoolField, EmbeddedField
+from jsonmodels.fields import StringField, BoolField, EmbeddedField, ListField
 from jsonmodels.models import Base
 
 from apiserver.apimodels import DictField, callable_default
@@ -30,3 +30,4 @@ class GetSupportedModesResponse(Base):
     basic = EmbeddedField(BasicMode)
     server_errors = EmbeddedField(ServerErrors)
     sso = DictField([str, type(None)])
+    sso_providers = ListField([dict])

apiserver/schema/services/login.conf

@@ -63,6 +63,14 @@ supported_modes {
                         type: string
                     }
                 }
+                sso_providers {
+                    description: "The list of SSO authentication providers"
+                    type: array
+                    items {
+                        type: object
+                        additionalProperties: true
+                    }
+                }
                 server_errors {
                     description: "Server initialization errors"
                     type: object

apiserver/services/login/__init__.py

@@ -26,6 +26,7 @@ def supported_modes(_, __, ___: GetSupportedModesRequest):
     return GetSupportedModesResponse(
         basic=BasicMode(enabled=FixedUser.enabled(), guest=guest),
         sso={},
+        sso_providers=[],
         server_errors=ServerErrors(
             missed_es_upgrade=info.missed_es_upgrade,
             es_connection_error=info.es_connection_error,