Update Service Broker permissions based on Docker testing

Verified all documented permissions against SQL Server 2022 in Docker:
- Minimal runtime permissions (polling mode): SELECT/INSERT/DELETE on
  message tables + SELECT/UPDATE on id tables - verified each is
  individually necessary and collectively sufficient
- Service Broker permissions: Updated to recommend db_owner role since
  SqlDependency needs CONTROL ON SCHEMA::dbo to manage its temporary
  Service Broker objects (queue, service, stored procedure)
- Schema installation permissions: verified correct
- AutoEnableServiceBroker permission: verified correct

Agent-Logs-Url: https://github.com/IntelliTect/IntelliTect.AspNetCore.SignalR.SqlServer/sessions/e89277da-2d43-4215-a743-5700ccb78ff7

Co-authored-by: ascott18 <5017521+ascott18@users.noreply.github.com>

Author: Copilot

README.md

@@ -46,16 +46,23 @@ GRANT SELECT, INSERT, DELETE ON [SignalR].[Messages_YourHubName_0] TO [YourUser]
 GRANT SELECT, UPDATE ON [SignalR].[Messages_YourHubName_0_Id] TO [YourUser];
 ```
 
-If Service Broker is enabled and you want to use it for real-time notifications (instead of falling back to polling), additional permissions are required:
+If Service Broker is enabled and you want to use it for real-time notifications (instead of falling back to polling), the `SqlDependency` mechanism requires additional permissions to create and manage its temporary Service Broker objects. The simplest approach is to grant the `db_owner` role:
+
+``` sql
+EXEC sp_addrolemember 'db_owner', 'YourUser';
+```
+
+If `db_owner` is too broad, the following individual permissions are required at a minimum, though `SqlDependency` may still require `db_owner` in some environments:
 
 ``` sql
 -- Required for SqlDependency to subscribe to query notifications:
 GRANT SUBSCRIBE QUERY NOTIFICATIONS TO [YourUser];
 
--- Required for SqlDependency to create its temporary Service Broker objects:
+-- Required for SqlDependency to create and manage its temporary Service Broker objects in the dbo schema:
 GRANT CREATE PROCEDURE TO [YourUser];
 GRANT CREATE QUEUE TO [YourUser];
 GRANT CREATE SERVICE TO [YourUser];
+GRANT CONTROL ON SCHEMA::dbo TO [YourUser];
 GRANT REFERENCES ON CONTRACT::[http://schemas.microsoft.com/SQL/Notifications/PostQueryNotification] TO [YourUser];
 
 -- Required for receiving Service Broker error notifications: