SlackAutoJoinRule
A rule defining which Slack channels the Plain bot automatically joins, plus optional default channel options applied when a channel is connected via this rule.
SlackAutoJoinRuleFields
Null for legacy rules read from the prefix/suffix settings that have not
yet been saved through setSlackAutoJoinRules.
The workspace Slack channel integration this rule belongs to.
Plain joins any new Slack channel whose name starts with this string. Empty string means no prefix filter.
Plain joins any new Slack channel whose name ends with this string. Empty string means no suffix filter.
Null means the channel mode is detected automatically (current behaviour).
Null means the team default ingestion mode applies.

