Support fetching plugin dependencies

[pkosiec]

Description

Changes proposed in this pull request:

• Support fetching plugin dependencies
  • Download plugins and its dependencies with go-getter
  • Pass PLUGIN_DEPENDENCY_DIR env variable to the plugins to use fetched dependencies
• Fix plugin index validation
• Fix inconsistencies in gRPC API field naming

Testing

No need to test it manually - the current integration tests prove the functionality works as expected. Helm binary is no longer there in the Botkube Docker image, but the integration tests still pass.

However, if you'd like to, then follow the tutorial here: https://docs.botkube.io/plugin/local-testing

I used the following file as the /tmp/config-values.yaml:

plugins:
  repositories:
    botkube:
      url: http://localhost:8080/plugins-index.yaml

communications:
  "default-group":
    socketSlack:
      enabled: true
      appToken: "xapp-..."
      botToken: "xoxb-..."
      notification:
        type: "short"
      channels:
        "default":
          name: botkube-demo
          bindings:
            executors:

              - helm
            sources: []

executors:
  helm:
    botkube/helm:
      config:
        helmCacheDir: /tmp/helm/.cache
        helmConfigDir: /tmp/helm/
        helmDriver: secret
      enabled: true

In botkube repo, run:

npx serve --listen 8080

Then in a new terminal run:

export BOTKUBE_SETTINGS_LOG_LEVEL=info
export BOTKUBE_PLUGINS_CACHE__DIR="/tmp/plugins"
export BOTKUBE_CONFIG_PATHS="$(pwd)/resource_config.yaml,/tmp/config-values.yaml"
PLUGIN_DOWNLOAD_URL_BASE_PATH="http://localhost:8080/plugin-dist" make gen-plugins-index; rm -rf /tmp/plugins; go run cmd/botkube/main.go

I hope you have different Helm version installed on your system - if not, upgrade it locally to anything different than v3.6.3 (e.g. 3.10+) 😄
Once Botkube is run, run @Botkube helm version on the botkube-demo channel to see the Helm version used. The output should be equal to:

Related PRs:

kubeshop/botkube-docs#203

Related issue(s)

#899

[mszostok]

I have only minor comments, overall it LGTM