Auth via Gh App

[kommendorkapten]

This PR adds support for authenticating with a GitHub App instead of a PAT. If both are provided, the GitHub App takes precedence.

The used package for token management automatically takes care of token renewal, and is thread safe.

[Copilot]

Pull request overview

This PR adds GitHub App authentication support to the deployment tracker, allowing authentication via GitHub App credentials instead of only Personal Access Tokens (PATs). When both authentication methods are configured, the GitHub App takes precedence.

Changes:

• Added GitHub App authentication using the ghinstallation package for automatic token management
• Introduced three new environment variables for GitHub App configuration (app ID, installation ID, and private key path)
• Updated documentation to describe both PAT and GitHub App authentication methods

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
pkg/deploymentrecord/client.go	Added WithGHApp option and transport field; updated PostOne to prioritize GitHub App authentication
internal/controller/controller.go	Added logic to configure GitHub App client options when credentials are present
internal/controller/config.go	Added three new config fields for GitHub App credentials
go.mod	Added dependencies for GitHub App authentication (ghinstallation, golang-jwt, go-github)
cmd/deployment-tracker/main.go	Added environment variable loading for GitHub App credentials
README.md	Updated documentation with authentication section and GitHub App environment variables

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[indigok]

LGTM ✨