🆕 v4.1.0 🚀

Highlights

🐍 use viper for configuration management
- takes over the job of properly fetching and merging config options from
  - CLI arguments/flags
  - environment variables
  - config file
- this also fixes some issues with using the config file (like cobra defaults overriding config file values)
✔️ add JSON-Schema validation for the Simple config file schema
🆕 config version k3d.io/v1alpha2 (some naming changes)
- exposeAPI -> kubeAPI
- options.k3d.noRollback -> options.k3d.disableRollback
- options.k3d.prepDisableHostIPInjection -> options.k3d.disableHostIPInjection

add root flag --timestamps to enable timestamped logs
improved multi-server cluster support (#467)
- log a warning, if one tries to create a cluster with only 2 nodes (no majority possible, no fault tolerance)
- revamped cluster start procedure: init-node, sorted servers, agents, helpers
- different log messages per role and start-place (that we wait for to consider a node to be ready)
- module: NodeStartOpts now accept a ReadyLogMessage and NodeState now takes a Started timestamp string

do not ignore --no-hostip flag and don't inject hostip if --network=host (#471, @konradmalik)
fix: --no-lb ignored
fix: print error cause when serverlb fails to start

tests/e2e: add config override test
tests/e2e: add multi server start-stop cycle test
tests/e2e: improved logs with stage and test details.
builds&tests: use Docker 20.10 and BuildKit everywhere
📝 docs: add https://github.com/AbsaOSS/k3d-action (GitHub Action) as a related project (#476, @kuritka)

E2E Tests ran with k3s versions
- v1.17.17-k3s1 (see Known Issues below)
- v1.18.15-k3s1 (see Known Issues below)
- v1.19.7-k3s1
- v1.20.2-k3s1

automatic multi-server cluster restarts tend to fail with k3s versions v1.17.x & v1.18.x and probably earlier versions (using dqlite)
Using Viper brings us lots of nice features, but also one problem:
- We had to switch StringArray flags to StringSlice flags, which
  - allow to use multiple flag values comma-separated in a single flag, but also
  - split flag values that contain a comma into separate parts (and we cannot handle issues that arise due to this)
    - so if you rely on commas in your flag values (e.g. for --env X=a,b,c), please consider filing an issue or supporting spf13/viper#246 and spf13/viper#398
    - --env X=a,b,c would be treated the same as --env X=a, --env b, --env c