chore(deps): bump github.com/slack-go/slack from 0.17.3 to 0.21.1

[dependabot]

Bumps github.com/slack-go/slack from 0.17.3 to 0.21.1.

Release notes

Sourced from github.com/slack-go/slack's releases.

v0.21.1

Added

• MessageEvent channel type helpers — New ChannelTypeChannel, ChannelTypeGroup, ChannelTypeIM, and ChannelTypeMPIM constants plus IsChannel(), IsGroup(), IsIM(), and IsMpIM() convenience methods on MessageEvent. No more comparing raw strings to figure out where a message came from:

if ev.IsIM() {
    // handle direct message
}

Fixed

• MessageEvent doc typo — ChannelType documentation listed "mim" instead of the correct "mpim".
• Duplicate attachment/block serialization — MsgOptionAttachments and MsgOptionBlocks were serializing payloads twice (once for the response-URL JSON path, once for the form POST path). Serialization now happens once inside formSender.BuildRequestContext. (#1547)

[!NOTE] UnsafeApplyMsgOptions no longer includes attachments/blocks keys in the returned values, since marshalling is deferred to send time. This function is documented as unsupported.

v0.21.0

[!WARNING] This release contains multiple breaking changes. Please review the sections below before upgrading.

Breaking changes

Removed APIs

• IM struct removed — Use Conversation instead. IsUserDeleted has been moved there.
• Info.GetBotByID, GetUserByID, GetChannelByID, GetGroupByID, GetIMByID removed — These were deprecated and returned nil unconditionally. Remove any calls to them.

Signature changes

• ListReactions now uses cursor-based pagination — Returns ([]ReactedItem, string, error) instead of ([]ReactedItem, *Paging, error). ListReactionsParameters replaces Count/Page with Cursor/Limit.

  // Before
  items, paging, err := api.ListReactions(params)
  // After
  items, nextCursor, err := api.ListReactions(params)

• ListStars/GetStarred now use cursor-based pagination — Same pattern: returns string (next cursor) instead of *Paging. StarsParameters replaces Count/Page with Cursor/Limit.

• GetAccessLogs now uses cursor-based pagination — Same pattern: returns string (next cursor) instead of *Paging. AccessLogParameters replaces Count/Page with Cursor/Limit.

... (truncated)

Changelog

Sourced from github.com/slack-go/slack's changelog.

[0.21.1] - 2026-04-08

Added

• slackevents.ChannelType* constants and MessageEvent helpers — Added ChannelTypeChannel, ChannelTypeGroup, ChannelTypeIM, ChannelTypeMPIM constants and IsChannel(), IsGroup(), IsIM(), IsMpIM() methods on MessageEvent so callers no longer need to compare raw strings.

Fixed

• Duplicate attachment/block serialization in MsgOptionAttachments / MsgOptionBlocks — Attachments and blocks were serialized twice: once into typed struct fields (for the JSON response-URL path) and again into url.Values (for the form POST path). Serialization for the form path now happens inside formSender.BuildRequestContext, so each sender owns its own marshalling. This fixes the long-standing FIXME and eliminates redundant json.Marshal calls in the option functions. (#1547)

  [!NOTE] UnsafeApplyMsgOptions returns config.values directly. After this change, attachments and blocks keys are no longer present in those values since marshalling is deferred to send time. This function is documented as unsupported.

[0.21.0] - 2026-04-05

Deprecated

• slackevents.ParseActionEvent — Cannot parse block_actions payloads (returns unmarshalling error). Use slack.InteractionCallback with json.Unmarshal instead, or slack.InteractionCallbackParse for HTTP requests. InteractionCallback handles all interaction types. (#596)
• slackevents.MessageAction, MessageActionEntity, MessageActionResponse — Associated types that only support legacy interactive_message payloads.

Removed

• IM struct — Removed the IM struct (and unused internal types imChannel, imResponseFull). The IsUserDeleted field has been moved to Conversation, where it is populated for IM-type conversations. Code using IM should switch to Conversation.

  [!NOTE] In practice no user should be affected — IM was never returned by any public API method in this library, so there was no way to obtain one outside of manual construction.

• Info.GetBotByID, GetUserByID, GetChannelByID, GetGroupByID, GetIMByID — These methods were deprecated and returned nil unconditionally. They have been removed.

  [!WARNING] Breaking change. If you are calling any of these methods, remove those calls — they were already no-ops.

... (truncated)

Commits

• 6d77e45 chore: v0.21.1
• b1e976f chore(slackevents): clarify eventsMap priority and remove stale TODOs
• 923f351 feat(slackevents): add ChannelType constants and helpers
• 17153aa chore: remove stale TODO
• fa3e143 chore: assert the test file and comment
• 7ec6a51 chore: assert the test file as well
• 5e0d5c3 chore: remove misleading XXX prefix to an excellent comment
• 3500739 chore: better Icons godoc
• 9f9002a chore: remove useless TODO
• ecb7c68 chore: remove useless TODO
• Additional commits viewable in compare view

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