Fix Github service bugs

[malhotra5]

End-user friendly description of the problem this fixes or functionality that this introduces

• Include this change in the Release Notes. If checked, you must provide an end-user friendly description for your change below

---

Give a summary of what the PR does, explaining any non-trivial design decisions

This PR fixes a group of bugs. NOTE: this doesn't affect any existing functionality. However, these changes are blocking for implementing token refresh logic

The bugs fixed

1. Headers should be dynamically generated (due to token refresh)
2. App mode comparison is always false (replace "SAAS" with AppMode.SAAS)
3. Bad response for get_installation_ids function means a dict object isn't return. This PR handles this edge case appropriately
4. We should use fetch_response to call APIs that require refresh token logic (this PR fixed one such case where get_user was used in place of fetch_response('get_user')

---

Link of any specific issues this addresses

---

To run this PR locally, use the following command:

docker run -it --rm   -p 3000:3000   -v /var/run/docker.sock:/var/run/docker.sock   --add-host host.docker.internal:host-gateway   -e SANDBOX_RUNTIME_CONTAINER_IMAGE=docker.all-hands.dev/all-hands-ai/runtime:8d314e3-nikolaik   --name openhands-app-8d314e3   docker.all-hands.dev/all-hands-ai/openhands:8d314e3

[rbren]

Suggested change

	return []
	return {}

right?

[rbren]

or maybe we want isinstance(data, list)?

[malhotra5]

I believe the code is correct; the Github API returns a dict

data = {"installations": [{"id": 3}], "app_slug": .....}

The frontend expects the list of just installation IDs, however, so we return data.get('installations', [])

The return statement of this function reflects this requirement

[rbren]

Oh I see it now, thanks