chore: groundwork for multi-user to server

[SamMorrowDrums]

In order to facilitate multi-user (MCP Host) to server communication, we need to support new *github.Client clients per request, rather than globally.

This change is a NOOP that makes it possible.

[Copilot]

Pull Request Overview

This PR lays the groundwork for multi‐user support by updating all GitHub client calls to accept a function returning a per-request GitHub client instead of a global client. Key changes include modifying tool/resource handler function signatures, updating tests to wrap the client in a closure, and propagating these changes across resources, pull requests, issues, and code scanning tools.

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated no comments.

File	Description
pkg/github/server_test.go	Updated GetMe call to use a client-returning lambda.
pkg/github/server.go	Introduced a getClient function to extract authToken from context and used it for all GitHub client invocations.
pkg/github/search*.go, repositories*.go, pullrequests*.go, issues*.go, code_scanning*.go	Updated function signatures and calls to pass a getClient closure, ensuring per-request client configuration.

Comments suppressed due to low confidence (1)

pkg/github/server.go:21

• [nitpick] Consider extracting the string literal "authToken" into a named constant to improve clarity and maintainability in contexts where it's used.

authToken, ok := ctx.Value("authToken").(string)

[juruen]

should we create a type with this function signature?

[SamMorrowDrums]

Yeah, I knew I should really - not hard to fix.

[williammartin]

Approved but minor request. Happy for you to bypass under the assumption you just address this if you make any changes!

[williammartin]

If you wouldn't mind I think a lot of noise could go away with:

func stubGetClientFn(client *github.Client) GetClientFn {
	return func(_ context.Context) (*github.Client, error) {
		return client, nil
	}
}

func Test_GetMe(t *testing.T) {
	// Verify tool definition
	mockClient := github.NewClient(nil)
	tool, _ := GetMe(stubGetClientFn(mockClient), translations.NullTranslationHelper)
...

Or perhaps:

func stubbedGetClientFn() GetClientFn {
	return func(_ context.Context) (*github.Client, error) {
		return github.NewClient(nil), nil
	}
}

func Test_GetMe(t *testing.T) {
	// Verify tool definition
	tool, _ := GetMe(stubbedGetClientFn(), translations.NullTranslationHelper)
...

Slight preference for the former because it's clearer how the client is being injected.

[williammartin]

Made minor edit to names above, just in case you'd already read it.