Fix Linear Personal Access Token (PAT) client initialization using apiKey instead of accessToken

[agerlic]

Fix LinearClient initialization to match Linear SDK documentation

This PR fixes an issue with the LinearClient initialization in the Personal Access Token (PAT) flow. According to the Linear SDK documentation, when using API key authentication, the client should be initialized with the apiKey parameter rather than the accessToken parameter.

[agerlic]

FYI @ocasta181

[ngub]

Spent some time debugging the following error:

GraphQL operation failed: It looks like you're trying to use an API key as a Bearer token. Remove the Bearer prefix from the Authorization header.

Here's the exact place in the Linear SDK that produces it: https://github.com/linear/linear/blob/master/packages/sdk/src/client.ts#L34

I came up with the same solution as in the PR, would love to see it merged 🙏

[SvenMeyer]

@agerlic @ngub
I actually implemented the same fix, even made a pull request (#10) which I deleted when I checked thereafter the outstanding pull requests.
After some review it looks like that #3 fixed the authentication issue and some other issues.
There was just one error which I fixed and bundled into a new pull request #11
Authentication with an API key should work now.

You may want to test that and provide feedback.

Maybe it even allows now OAuth, I saw some code in #3 , but I haven't tested it myself.

[ocasta181]

Hey, thanks for the contribution @agerlic!