docs(plugin): SOPS Kustomize Generator Plugin

Signed-off-by: Pedro Tôrres <t0rr3sp3dr0@gmail.com>

README.md

@@ -1,2 +1,99 @@
-# sops-kustomize-generator-plugin
-SOPS Kustomize Generator Plugin
+# SOPS Kustomize Generator Plugin
+It is a plugin for [Kustomize](https://github.com/kubernetes-sigs/kustomize) that allows you to use Kubernetes Secrets encrypted with [SOPS](https://github.com/mozilla/sops) as a generator.
+
+## Getting Started
+
+### Install
+To install this plugin on Kustomize, download the binary to Kustomize Plugin folder with `apiVersion: inloco.com.br/v1` and `kind: SOPS`. Then make it executable.
+
+#### Linux 64-bits
+```bash
+PLACEMENT=${XDG_CONFIG_HOME:-$HOME/.config}/kustomize/plugin/inloco.com.br/v1/sops
+
+mkdir -p $PLACEMENT
+
+PLUGIN=$PLACEMENT/SOPS
+
+wget -O $PLUGIN https://github.com/inloco/sops-kustomize-generator-plugin/releases/download/v1.0.0/plugin-linux-amd64
+
+chmod +x $PLUGIN
+```
+
+#### macOS 64-bits
+```bash
+PLACEMENT=${XDG_CONFIG_HOME:-$HOME/.config}/kustomize/plugin/inloco.com.br/v1/sops
+
+mkdir -p $PLACEMENT
+
+PLUGIN=$PLACEMENT/SOPS
+
+wget -O $PLUGIN https://github.com/inloco/sops-kustomize-generator-plugin/releases/download/v1.0.0/plugin-darwin-amd64
+
+chmod +x $PLUGIN
+```
+
+#### Manual Build and Install for Other Systems and/or Architectures
+```bash
+git clone https://github.com/inloco/sops-kustomize-generator-plugin
+
+cd sops-kustomize-generator-plugin
+
+go get -d -v ./...
+
+go build -a -installsuffix cgo -ldflags '-extldflags "-static" -s -w' -tags netgo -v ./...
+
+PLACEMENT=${XDG_CONFIG_HOME:-$HOME/.config}/kustomize/plugin/inloco.com.br/v1/sops
+
+mkdir -p $PLACEMENT
+
+mv ./sops-kustomize-generator-plugin $PLACEMENT/SOPS
+
+cd ..
+
+rm -fR sops-kustomize-generator-plugin
+```
+
+### Using
+
+We can start with a regular Kubernetes Secret in its YAML format.
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: mysecret
+type: Opaque
+data:
+  username: YWRtaW4=
+  password: MWYyZDFlMmU2N2Rm
+```
+
+To convert it to a file that will be processed by the plugin, we replace `apiVersion: v1` with `apiVersion: inloco.com.br/v1` and `kind: Secret` with `kind: SOPS`.
+```yaml
+apiVersion: inloco.com.br/v1
+kind: SOPS
+metadata:
+  name: mysecret
+type: Opaque
+data:
+  username: YWRtaW4=
+  password: MWYyZDFlMmU2N2Rm
+```
+
+Finally we encrypt it using SOPS with the following command:
+```bash
+sops --encrypt --encrypted-regex '^(data|stringData)$' --in-place ./secret.yaml
+```
+
+Now we can specify `./secret.yaml` as a generator on `kustomization.yaml`:
+```yaml
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+generators:
+  - ./secret.yaml
+```
+
+## Notes
+- Remember to use `--enable_alpha_plugins` flag when running `kustomize build`.
+- You may need to use environment variables, such as `AWS_PROFILE`, to configure SOPS decryption when running Kustomize.
+- Integrity checks are disabled on SOPS decryption, this is done to prevent integrity failures due to Kustomize sortting the keys of original YAML file.
+- This documentation assumes that you are familiar with [Kustomize](https://github.com/kubernetes-sigs/kustomize) and [SOPS](https://github.com/mozilla/sops), read their documentation if necessary.