Normalize and validate channel names and IDs

[pkosiec]

Description

Changes proposed in this pull request:

• Normalize and validate channel names and IDs

Testing

No need to test it - validation and normalization is covered by tests. But if you want to:

Use this config:

communications:
  "default-group":
    socketSlack:
      enabled: true
      appToken: "xapp-..."
      botToken: "xoxb-...."
      channels:
        "default":
          name: "AWdaDAsad" # <-- you can do here a mistake
          bindings:
            executors:
              - k8s-default-tools
            sources:
              - k8s-all-events
        "secondary":
          name: priv-channel
          bindings:
            executors: []
            sources: []

    discord:
      enabled: true
      botID: "..."
      token: "..."
      channels:
        'default':
          id: "..."
          bindings:
            executors:
              -  k8s-default-tools
            sources:
              - k8s-all-events
        'test':
          id: "..."
          bindings:
            executors:
              - k8s-default-tools
            sources:
              - k8s-all-events
        'test2':
          id: "..."
          bindings:
            executors:
              -  k8s-default-tools
            sources:
              - k8s-all-events

    mattermost:
      enabled: true
      botName: Botkube
      team: team
      token: ...
      url: https://team.cloud.mattermost.com
      channels:
        'default':
          name: "general"
          bindings:
            executors:
              - k8s-default-tools
            sources:
              - k8s-all-events
              - k8s-recommendation-events
      notification:
        type: short

export KUBECONFIG="/path/to/kubeconfig"
export BOTKUBE_SETTINGS_LOG_LEVEL=info
export BOTKUBE_PLUGINS_CACHE__DIR="/tmp/plugins"
export BOTKUBE_SETTINGS_KUBECONFIG=$KUBECONFIG
export BOTKUBE_CONFIG_PATHS="$(pwd)/helm/botkube/values.yaml,$(pwd)/comm_config.yaml"
go run ./cmd/botkube-agent/main.go

[mszostok]

LGTM