Add flux executor plugin with GitHub support

[mszostok]

Description

Changes proposed in this pull request:

• Add flux executor plugin with GitHub support

Testing

1. Checkout this PR
2. Create k3d cluster: k3d cluster create labs --image=rancher/k3s:v1.25.0-k3s1
3. Create GitHub token: https://github.com/settings/personal-access-tokens/new
4. Create configuration:

   communications:
     default-group:
       socketSlack:
         enabled: true
         channels:
           default:
             name: random
             bindings:
               sources: []
               executors:
                 - flux
         appToken: "xapp-1"
         botToken: "xoxb-"
   
   executors:
     flux:
       botkube/flux:
         enabled: true
         config:
           log:
             level: "debug"
           github:
             auth:
               accessToken: "ghp_"
   
         context:
           rbac:
             group:
               type: Static
               static:
                 values: [ "system:masters" ]
    
   extraEnv:
     - name: LOG_LEVEL_EXECUTOR_BOTKUBE_FLUX
       value: "debug"
   
   plugins:
     cacheDir: "/tmp/plugins"
     repositories:
       botkube:
         url: http://host.k3d.internal:3010/botkube.yaml
   
   settings:
     log:
       level: "debug"
       formatter: text
     clusterName: "labs"
     upgradeNotifier: false
   
   analytics:
     disable: true
   
   configWatcher:
     enabled: false
   

5. Build plugin: PLUGIN_TARGETS="flux" make build-plugins
6. Start plugin server: env PLUGIN_SERVER_HOST=http://host.k3d.internal go run test/helpers/plugin_server.go
7. Install Botkube:

   helm upgrade botkube --install --namespace botkube ./helm/botkube --create-namespace -f /tmp/flux-config.yaml --set image.repository=kubeshop/pr/botkube --set image.pullPolicy="Always" --set image.tag=1170-PR

Flux

1. Run @Botkube flux tutorial

2. Click flux install

3. Next navigate to terminal and create:

   apiVersion: source.toolkit.fluxcd.io/v1
   kind: GitRepository
   metadata:
     name: podinfo
   spec:
     interval: 5m
     url: https://github.com/mszostok/podinfo
     ref:
       branch: master
   ---
   apiVersion: kustomize.toolkit.fluxcd.io/v1
   kind: Kustomization
   metadata:
     name: podinfo
   spec:
     interval: 10m
     targetNamespace: default
     sourceRef:
       kind: GitRepository
       name: podinfo
     path: "./kustomize"
     prune: true
     timeout: 1m

   kubectl apply -f podinfo.yaml -n flux-system

4. Run on Slack:

   • @Botkube flux get ks
   • @Botkube flux get source git
   • @Botkube flux diff ks podinfo --path ./kustomize --github-ref 3
   • @Botkube flux diff ks podinfo --path ./kustomize --github-ref https://github.com/mszostok/podinfo/pull/2

   Play with buttons.

Related issue(s)

• Flux CD Executor Plugin #1016

[huseyinbabal]

LGTM with minor comments, really good job ! 🚀