Refactor groupware service after ADR decision on the Groupware API

* after having decided that the Groupware API should be a standalone
   independent custom REST API that is using JMAP data models as much as
   possible,
 * removed Groupware APIs from the Graph service
 * moved Groupware implementation to the Groupware service, and
   refactored a few things accordingly

services/proxy/pkg/config/defaults/defaultconfig.go

@@ -292,9 +292,8 @@ func DefaultPolicies() []config.Policy {
 					SkipXAccessToken: true,
 				},
 				{
-					Endpoint:    "/groupware",
-					Service:     "eu.opencloud.web.groupware",
-					Unprotected: true,
+					Endpoint: "/groupware",
+					Service:  "eu.opencloud.web.groupware",
 				},
 				{
 					Endpoint:    "/auth",