feat(experiment): add apps.icon.set support for non-hosted app icons

[srtaalej]

Changelog

No user-facing changes until apps.icon.set endpoint is live

Summary

This PR adds IconSet() API method targeting the apps.icon.set endpoint for non-hosted (Bolt) app icons. Gated behind the set-icon experiment flag (--experiment=set-icon) (see Note)

Expected Behavior / Test Plan

slack deploy → updateIcon() uses Icon() (no experiment needed, hosted apps, existing behavior)
slack deploy --experiment set-icon → updateIcon() uses IconSet() (both app types)
slack run --experiment set-icon → InstallLocalApp icon block runs via IconSet() (both app types)
slack run (no experiment) → no icon upload

Migration plan

When apps.icon.set is generally available:

1. Remove the set-icon experiment gate from updateIcon and InstallLocalApp
2. Replace all Icon() calls with IconSet()
3. Delete the deprecated Icon() method, its tests, mock, and the apps.hosted.icon constant

Note

🔴 The apps.icon.set endpoint is available under a toggle. No changes were made to the existing apps.hosted.icon flow.
Required scope (app_configurations:write) may be subject to change before the endpoint goes public

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

❌ Patch coverage is 26.08696% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.15%. Comparing base (dd3d92e) to head (7b30774).

Files with missing lines	Patch %	Lines
internal/pkg/apps/install.go	0.00%	16 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #469      +/-   ##
==========================================
- Coverage   71.23%   71.15%   -0.08%     
==========================================
  Files         222      222              
  Lines       18664    18684      +20     
==========================================
  Hits        13295    13295              
- Misses       4189     4207      +18     
- Partials     1180     1182       +2     

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[zimeg]

🐣 A few quick comments and questions and I'm excited to test this next!

[zimeg]

@srtaalej Right now I'm not having luck with this when testing in a shared team sandbox and the error isn't so obvious to me...

Let me know if this is something perhaps with the image I use? I'll include it here for testing and other reviewers:

[zimeg]

🔬 issue: This outputs a warning to verbose logs and it's not clear what I might not be including?

uploading icon
icon error: https://slack.com/api/apps.icon.set error: missing_arguments
   Error updating app icon: https://slack.com/api/apps.icon.set error: missing_arguments
   Finished in 0.7s

[srtaalej]

are you uploading through the manifest or is the image just in the root of the project?

[zimeg]

@srtaalej I saved this file to the root of the project 🌲 ✨

[srtaalej]

the "file" fielf for the api request had the wrong name! can you try again ?