Currently the most "secret" way to specify the oidc client secret is via
an environment variable `OIDC_CLIENT_SECRET`, which is problematic[1].
Lets allow reading oidc client secret from a file. For extra convenience
the path to the secret will resolve the environment variables.
[1]: https://systemd.io/CREDENTIALS/
* Port OIDC integration tests to v2
* Move Tailscale old versions to TS2019 list
* Remove Alpine Linux container
* Updated changelog
* Releases: use flavor to set the tag suffix
* Added more debug messages in OIDC registration
* Added more logging
* Do not strip nodekey prefix on handle expired
* Updated changelog
* Add WithHostnameAsServerURL option func
* Reduce the number of namespaces and use hsic.WithHostnameAsServerURL
* Linting fix
* Fix linting issues
* Wait for ready outside the up goroutine
* Minor change in log message
* Add prefix to env var
* Remove unused env var
Co-authored-by: Juan Font <juan.font@esa.int>
Co-authored-by: Steven Honson <steven@honson.id.au>
Co-authored-by: Kristoffer Dalby <kristoffer@dalby.cc>
