chore(deps): bump github.com/slack-go/slack from 0.14.0 to 0.15.0 (#203)

* chore(deps): bump github.com/slack-go/slack from 0.14.0 to 0.15.0

Bumps [github.com/slack-go/slack](https://github.com/slack-go/slack) from 0.14.0 to 0.15.0.
- [Release notes](https://github.com/slack-go/slack/releases)
- [Changelog](https://github.com/slack-go/slack/blob/master/CHANGELOG.md)
- [Commits](slack-go/slack@v0.14.0...v0.15.0)

---
updated-dependencies:
- dependency-name: github.com/slack-go/slack
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

* fix(slack): switch to "V2" upload API

As can be seen [when updating `slack-go`][run], the current API is
deprecated and we need to update to continue working beyond May 2025.

[run]: https://github.com/grafana/flagger-k6-webhook/actions/runs/11342664073/job/31543572688?pr=203

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Iain Lane <iain@grafana.com>

go.mod

@@ -9,7 +9,7 @@ require (
 	github.com/google/uuid v1.6.0
 	github.com/prometheus/client_golang v1.20.4
 	github.com/sirupsen/logrus v1.9.3
-	github.com/slack-go/slack v0.14.0
+	github.com/slack-go/slack v0.15.0
 	github.com/stretchr/testify v1.9.0
 	github.com/urfave/cli/v2 v2.27.5
 	k8s.io/api v0.31.1

go.sum

@@ -97,8 +97,8 @@ github.com/russross/blackfriday/v2 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
 github.com/sirupsen/logrus v1.9.3 h1:dueUQJ1C2q9oE3F7wvmSGAaVtTmUizReu6fjN8uqzbQ=
 github.com/sirupsen/logrus v1.9.3/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
-github.com/slack-go/slack v0.14.0 h1:6c0UTfbRnvRssZUsZ2qe0Iu07VAMPjRqOa6oX8ewF4k=
-github.com/slack-go/slack v0.14.0/go.mod h1:hlGi5oXA+Gt+yWTPP0plCdRKmjsDxecdHxYQdlMQKOw=
+github.com/slack-go/slack v0.15.0 h1:LE2lj2y9vqqiOf+qIIy0GvEoxgF1N5yLGZffmEZykt0=
+github.com/slack-go/slack v0.15.0/go.mod h1:hlGi5oXA+Gt+yWTPP0plCdRKmjsDxecdHxYQdlMQKOw=
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
 github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=

pkg/slack/client.go

@@ -45,13 +45,13 @@ func (w *slackClientWrapper) UpdateMessages(slackMessages map[string]string, tex
 
 func (w *slackClientWrapper) AddFileToThreads(slackMessages map[string]string, fileName, content string) error {
 	for channelID, ts := range slackMessages {
-		fileParams := slack.FileUploadParameters{
+		fileParams := slack.UploadFileV2Parameters{
 			Title:           fileName,
 			Content:         content,
-			Channels:        []string{channelID},
+			Channel:         channelID,
 			ThreadTimestamp: ts,
 		}
-		if _, err := w.client.UploadFile(fileParams); err != nil {
+		if _, err := w.client.UploadFileV2(fileParams); err != nil {
 			return fmt.Errorf("error while uploading output to %s in slack channel %s: %w", ts, channelID, err)
 		}
 	}