docs: Usage on Podman

Author: otaviof

docs/container-image.md

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+`rhtap-cli`: Container Image
+----------------------------
+
+# Abstract
+
+The `rhtap-cli` container image is a portable and easy-to-use tool to deploy RHTAP (Red Hat Trusted Application Pipeline) from a container manager running on your local machine. The container image is designed to enable the deployment process on Kubernetes Jobs, ArgoCD (GitOps), and other container orchestration tools.
+
+
+# Usage
+
+The installer needs access to the target OpenShift/Kubernetes instance, therefore you either need to mount the local `~/.kube/config` file or provide the necessary environment variables to authenticate with the target cluster.
+
+## Podman
+
+For the `rhtap-cli integration github-app` you need to expose the callback port, used on the GitHub App registration, to the container. The GitHub App registration requires a personal access token, which should be created for the specific organization RHTAP will work on. In the example below, the token is passed as an environment variable `RHTAP_GITHUB_TOKEN`.
+
+The OpenShift configuration and credentials are passed to the container by mounting the local `~/.kube` directory to the container's `/root/.kube` directory. And the user `root` is employed to avoid permission issues, although the mounted directory is read-only.
+
+A interactive shell is started in the container, where you can run the `rhtap-cli` commands.
+
+```bash
+podman run \
+    --name="rhtap-cli" \
+    --rm \
+    --interactive \
+    --tty \
+    --env="RHTAP_GITHUB_TOKEN=${RHTAP_GITHUB_TOKEN}" \
+    --publish="127.0.0.1:8228:8228" \
+    --entrypoint="/bin/bash" \
+    --user="root" \
+    --volume="${HOME}/.kube:/root/.kube:ro" \
+    ghcr.io/redhat-appstudio/rhtap-cli:latest
+```
+
+Before the installation you should review the [`config.yaml`](../README.md#configuration) file to decide what's appropriate for your environment, in this example we are using the default configuration.
+
+In the container, you can run the `rhtap-cli` commands, for example, creating a GitHub App integration on the organization `rhtap-ex`, and using the same name for the GitHub App:
+
+```bash
+rhtap-cli integration github-app \
+    --config="config.yaml" \
+    --create \
+    --token="${RHTAP_GITHUB_TOKEN}" \
+    --org="rhtap-ex" \
+    --webserver-addr="0.0.0.0" \
+    rhtap-ex
+```
+
+After configuring the integrations, you can proceed with the deployment:
+
+```bash
+rhtap-cli deploy
+```