Add channel/channel_id in slack properties

[igoritos22]

There may be some situations where it is necessary to pass a specific channel in the slack message post. It would be interesting to have something like this:

  slack:
    # -- Slack Webhook URL (ex: <https://hooks.slack.com/services/XXXX/YYYY/ZZZZ>), if not `empty`, Slack output is *enabled*
    webhookurl: ""
    # -- Slack Footer
    channel: ""
    # -- Channel ID
    footer: ""
    # -- Slack icon (avatar)
    icon: ""
    # -- Slack username
    username: ""
    # -- `all` (default), `text` (only text is displayed in Slack), `fields` (only fields are displayed in Slack)
    outputformat: "all"
    # -- minimum priority of event to use this output, order is `emergency\|alert\|critical\|error\|warning\|notice\|informational\|debug or ""`
    minimumpriority: ""
    # -- a Go template to format Slack Text above Attachment, displayed in addition to the output from `slack.outputformat`. If empty, no Text is displayed before Attachment
    messageformat: ""

[Issif]

I'll add the feature asap.

[Issif]

the PR is merged, it will be in next release

[poiana]

Issues go stale after 90d of inactivity.

Mark the issue as fresh with /remove-lifecycle stale.

Stale issues rot after an additional 30d of inactivity and eventually close.

If this issue is safe to close now please do so with /close.

Provide feedback via https://github.com/falcosecurity/community.

/lifecycle stale

[poiana]

Stale issues rot after 30d of inactivity.

Mark the issue as fresh with /remove-lifecycle rotten.

Rotten issues close after an additional 30d of inactivity.

If this issue is safe to close now please do so with /close.

Provide feedback via https://github.com/falcosecurity/community.

/lifecycle rotten