Provisioning: Implement connection repositories endpoint for GitHub

This change implements the `/repositories` subresource endpoint for Connection
resources, enabling listing of repositories accessible through a GitHub App
connection.

Changes:
- Add ListRepositories method to Connection interface
- Add ListInstallationRepositories to GitHub Client interface
- Implement GitHub client method to list installation repositories
  - Creates installation access token from JWT
  - Handles pagination up to 1000 repos
- Implement ListRepositories in GitHub Connection
- Update connectionRepositoriesConnector to use Connection.ListRepositories
- Add ConnectionGetter interface and GetConnection method to APIBuilder
- Add comprehensive tests for the new functionality

apps/provisioning/pkg/connection/github/client.go

@@ -22,6 +22,19 @@ type Client interface {
 	// Apps and installations
 	GetApp(ctx context.Context) (App, error)
 	GetAppInstallation(ctx context.Context, installationID string) (AppInstallation, error)
+
+	// Repositories
+	ListInstallationRepositories(ctx context.Context, installationID string) ([]Repository, error)
+}
+
+// Repository represents a GitHub repository accessible through an installation.
+type Repository struct {
+	// Name of the repository
+	Name string
+	// Owner is the user or organization that owns the repository
+	Owner string
+	// URL of the repository (HTML URL)
+	URL string
 }
 
 // App represents a Github App.
@@ -91,3 +104,68 @@ func (r *githubClient) GetAppInstallation(ctx context.Context, installationID st
 		Enabled: installation.GetSuspendedAt().IsZero(),
 	}, nil
 }
+
+const (
+	maxRepositories = 1000 // Maximum number of repositories to fetch
+)
+
+// ListInstallationRepositories lists all repositories accessible by the specified GitHub App installation.
+// It first creates an installation access token using the JWT, then uses that token to list repositories.
+func (r *githubClient) ListInstallationRepositories(ctx context.Context, installationID string) ([]Repository, error) {
+	id, err := strconv.ParseInt(installationID, 10, 64)
+	if err != nil {
+		return nil, fmt.Errorf("invalid installation ID: %s", installationID)
+	}
+
+	// Create an installation access token
+	installationToken, _, err := r.gh.Apps.CreateInstallationToken(ctx, id, nil)
+	if err != nil {
+		var ghErr *github.ErrorResponse
+		if errors.As(err, &ghErr) && ghErr.Response.StatusCode == http.StatusServiceUnavailable {
+			return nil, ErrServiceUnavailable
+		}
+		return nil, fmt.Errorf("create installation token: %w", err)
+	}
+
+	// Create a new client with the installation token
+	tokenClient := github.NewClient(nil).WithAuthToken(installationToken.GetToken())
+
+	var allRepos []Repository
+	opts := &github.ListOptions{
+		Page:    1,
+		PerPage: 100,
+	}
+
+	for {
+		result, resp, err := tokenClient.Apps.ListRepos(ctx, opts)
+		if err != nil {
+			var ghErr *github.ErrorResponse
+			if errors.As(err, &ghErr) && ghErr.Response.StatusCode == http.StatusServiceUnavailable {
+				return nil, ErrServiceUnavailable
+			}
+			return nil, fmt.Errorf("list repositories: %w", err)
+		}
+
+		for _, repo := range result.Repositories {
+			allRepos = append(allRepos, Repository{
+				Name:  repo.GetName(),
+				Owner: repo.GetOwner().GetLogin(),
+				URL:   repo.GetHTMLURL(),
+			})
+		}
+
+		// Check if we've exceeded the maximum allowed repositories
+		if len(allRepos) > maxRepositories {
+			return nil, fmt.Errorf("too many repositories to fetch (more than %d)", maxRepositories)
+		}
+
+		// If there are no more pages, break
+		if resp.NextPage == 0 {
+			break
+		}
+
+		opts.Page = resp.NextPage
+	}
+
+	return allRepos, nil
+}