Handle GitHub installation Suspension

### Is your feature request related to a problem? Please describe.

The GitHub integration with Flagsmith does not handle the scenario where a user suspends the GitHub app.

### Describe the solution you'd like.

When a user wants to suspend the app, store that change in Flagsmith.

### Describe alternatives you've considered

Create a new column, in the table, that allows storing the suspended state of the GitHub app.

### Additional context

Handle, similar to uninstallation, to be done either from Flagsmith or from the app configuration in GitHub.