Add support of inputChannelId on sentry_metric_alert

[geototti21]

👋 Hey

I am trying to create a new sentry_metric_alert that has as action a Slack alert.

It is failing with getting the status of the metric alert creation from Sentry took too long, and I believe it is because of the rate limits from Slack. Docs say to also pass the Slack channelID to avoid that.

I can see that inputChannelId is already specified on the go-sentry client, so I believe we need to expose this from the terraform provider as well so it will look like this:

  trigger {
    action {
      type              = "slack"
      target_type       = "specific"
      target_identifier = "#alert-channel"
      # new field needed below
      input_channel_id  = "C0XXXXXXXXX"
      integration_id    = data.sentry_organization_integration.slack.id
    }
    alert_threshold = 300
    label           = "critical"
    threshold_type  = 0
  }

Please let me know what you think. 😄

[jianyuan]

The input_channel_id is now available in v0.12.0!