• Extension version: 0.12.0
• VSCode Version: 1.40.0-insider
• OS: Osx
• Github Enterprise version: GitHub Enterprise Server 2.16.12

Steps to Reproduce:

1. Login with github enterprise
2. See the log message

[Info] https://github.[company].org/api/v3: GraphQL not supported (Network error: Response not successful: Received status code 404)

I think this is related to #947

This is caused by invalid graphQL URL for the enterprise version. The reason is that this function will fallback to /api/v3 for URL other than github.com

But when constructing the ApolloClient, it append the base url with /graphql. which the URL now becomes /api/v3/graphql. That's why it returns 404.

Before fixing this, I couldn't create a pending PR review and comments. New comments was immediately posted as single comments (not as part of the pending review). I believe this is because it's using the REST API instead of the graphQL underneath.

How ever, once i use the correct graphQL URL. Loading Description page of PR no longer works. Got error with this

[Debug 130796s 117ms] PullRequestOverviewPanel> initialized without PR
[Debug 130796s 320ms] GitHubRepository> Fetch available merge methods - done
[Debug 130796s 328ms] GithubRepository> Unable to fetch PR: Error: GraphQL error: Field 'isDraft' doesn't exist on type 

Not sure why that is. But at least now I can use Draft PR functionalities