Update docs

Makefile

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+SHELL := /bin/bash
+.ONESHELL:
+.SHELLFLAGS = -ec
+RUN_ARGS := $(wordlist 2,$(words $(MAKECMDGOALS)),$(MAKECMDGOALS))
+
+
+help:
+	@grep -E '^[a-zA-Z_-]+:.*##' $(MAKEFILE_LIST) | \
+	awk -F '##' '{printf "  %-15s %s\n", $$1, $$2}'
+
+.PHONY:
+prepare-airgapped-cluster: ## for airgapped-tests
+	./scripts/dev/prepare_airgapped_cluster.sh
+
+.PHONY:
+cluster: ## creates a k3d cluster suitable for GOP
+	./scripts/init-cluster.sh $(RUN_ARGS)
+
+.PHONY:
+prepare-two-registries: ## for testing with multiple registries
+	./scripts/dev/prepare_two_registries.sh
+
+%:
+	@:

docs/Deploy-Ingress-Controller.md

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+# Ingress Controller
+
+In the default installation the GitOps-Playground comes without an Ingress-Controller.  
+
+We use Traefik as default Ingress-Controller.
+It can be enabled via the configfile or parameter `--ingress`.
+
+In order to make use of the ingress controller, it is recommended to use it in conjunction with `--base-url`, which will create `Ingress` objects for all components of the GitOps playground.
+
+The ingress controller is based on the helm chart [`ingress`](https://traefik.github.io/charts/).
+
+Additional parameters from this chart's values.yaml file can be added to the installation through the gitops-playground [configuration file](./Configuration.md).
+
+Example:
+```yaml
+features:
+  ingress:
+    active: true
+    helm:
+      values:
+        controller:
+          replicaCount: 4
+```
+In this Example we override the default `controller.replicaCount` (GOP's default is 2).
+
+This config file is merged with precedence over the defaults set by 
+* [the GOP](../argocd/cluster-resources/apps/ingress/templates/ingress-helm-values.ftl.yaml) and
+* [the charts itself](https://github.com/traefik/traefik-helm-chart/blob/master/traefik/values.yaml).
+
+# Deploy Ingresses
+
+It is possible to deploy `Ingress` objects for all components. You can either
+
+* set a common base url (`--base-url=https://example.com`) or
+* individual URLS: <- falsch!
+```
+--argocd-url https://argocd.example.com 
+--grafana-url https://grafana.example.com 
+--vault-url https://vault.example.com 
+--mail-url https://mail.example.com 
+--petclinic-base-domain petclinic.example.com 
+--nginx-base-domain nginx.example.com
+```
+* or both, where the individual URLs take precedence.
+
+Note: 
+* `jenkins-url` and `scmm-url` are for external services and do not lead to ingresses, but you can set them via `--base-url` for now.
+* In order to make use of the `Ingress` you need an ingress controller.
+  If your cluster does not provide one, the Playground can deploy one for you, via the `--ingress` parameter.
+* For this to work, you need to set an `*.example.com` DNS record to the externalIP of the ingress controller.
+
+Alternatively, [hyphen-separated ingresses](#subdomains-vs-hyphen-separated-ingresses) can be created,
+like http://argocd-example.com
+
+## Subdomains vs hyphen-separated ingresses
+
+* By default, the ingresses are built as subdomains of `--base-url`.  
+* You can change this behavior using the parameter `--url-separator-hyphen`.  
+* With this, hyphens are used instead of dots to separate application name from base URL.
+* Examples: 
+  * `--base-url=https://xyz.example.org`: `argocd.xyz.example.org` (default)  
+  * `--base-url=https://xyz.example.org`: `argocd-xyz.example.org` (`--url-separator-hyphen`)
+* This is useful when you have a wildcard certificate for the TLD, but use a subdomain as base URL.  
+  Here, browsers accept the validity only for the first level of subdomains.
+
+## Local ingresses
+
+The ingresses can also be used when running the playground on your local machine:
+
+* Ingresses might be easier to remember than arbitrary port numbers and look better in demos 
+* With ingresses, we can execute our [local clusters](./k3d.md) in higher isolation or multiple playgrounds concurrently
+* Ingresses are required [for running on Windows/Mac](./Running-on-Windows-Mac.md).
+
+To use them locally, 
+* init your cluster (`init-cluster.sh`).
+* apply your playground with the following parameters  
+  * `--base-url=http://localhost` 
+    * this is possible on Windows (tested on 11), Mac (tested on Ventura) or when using Linux with [systemd-resolved](https://www.freedesktop.org/software/systemd/man/systemd-resolved.service.html) (default in Ubuntu, not Debian)  
+      As an alternative, you could add all `*.localhost` entries to your `hosts` file.  
+      Use `kubectl get ingress -A` to get a full list 
+    * Then, you can reach argocd on `http://argocd.localhost`, for example
+  * `--base-url=http://local.gd` (or `127.0.0.1.nip.io`, `127.0.0.1.sslip.io`, or others)
+    * This should work for all other machines that have access to the internet without further config 
+    * Then, you can reach argocd on `http://argocd.local.gd`, for example
+* Note that when using port 80, the URLs are shorter, but you run into issues because port 80 is regarded as a privileged port.
+  Java applications seem not to be able to reach `localhost:80` or even `127.0.0.1:80` (`NoRouteToHostException`)
+* You can change the port using `init-cluster.sh --bind-ingress-port=8080`.  
+  When you do, make sure to append the same port when applying the playground: `--base-url=http://localhost:8080`
+* If your setup requires you to bind to a specific interface, you can just pass it with e.g. `--bind-ingress-port=127.0.0.1:80`