[BugBash][Portal] Issues with hub settings

### Describe the bug
Several issues with hub settings

### To Reproduce
#### Cannot edit hub setting after creating a new hub
1. Create a Web PubSub
2. Go to settings, click Add
3. Type a hub name, click Save
4. Continue to edit the hub, like update the hub name, add event handlers, but Save button is always disabled

This is even worse if the update failed, for example:
1. Type invalid url template, Save
2. Save will fail but I cannot save even after I fixed the url

#### What is valid hub name
1. Add a hub
2. In hub name, type `123`
3. It will tell me 123 is an invalid hub name, but I want to know what is a valid hub name

#### Delete a hub needs double confirm?
1. Select a hub and click Delete

Hub will be deleted without additional confirm, should we double confirm with user since delete is irreversible?

#### Unsaved changes alert if there is no unsaved change
1. Add a new hub, click Save
2. Click the close button on top right, it will warn me for unsaved changes, but actually there is no unsaved changes