feat: support Instagram collaborators on Reels, images, and carousels

[HafizMMoaz]

Summary

Instagram's Content Publishing API accepts a collaborators parameter
(up to 3 usernames) on media container creation. Without it, every Reel
published through TryPost needs a manual re-invite in the Instagram app
afterward - this covers the "smallest useful version" from the issue:
accept the field and pass it through to the container creation call.

Changes

• PostPlatformMetaRules::rules(): platforms.*.meta.collaborators
  (array, max 3, each entry a string up to 30 chars - Instagram's
  username length cap), following the exact shape suggested in the
  issue.
• InstagramPublisher: a withCollaborators() helper adds the field
  (JSON-encoded, matching Meta's expected format and the existing
  attached_media JSON-encoding pattern in FacebookPublisher) to
  whichever container actually gets published - single image, Reel, or
  the carousel's parent container (not per-item children, which
  don't accept it). Reads straight from $this->postPlatform->meta
  (same as other instance state already on the class) rather than
  threading a new parameter through every method, which also means it
  survives a carousel publish that resumes after an interruption - the
  parent container isn't created until the resume completes.
• publishStory() is untouched - Instagram doesn't support collaborators
  on Stories, so it's simply never added there.

What I intentionally left out

• Composer UI: the issue's suggested scope includes surfacing this
  in the web composer next to Pinterest's board picker etc. I didn't
  add it - it would be the first real usage of the TagsInput UI
  primitive in this app (everywhere else that needs an array-of-strings
  input, like Discord mentions, uses a server-side autocomplete instead),
  and I don't have a way to verify it renders/behaves correctly in a
  browser in this environment. Shipping an unverified new UI pattern
  felt riskier than leaving it for a follow-up where someone can
  actually click through it. The feature is fully usable today via the
  public API and MCP tools.
• Error-code mapping: the issue suggests mapping a specific Instagram
  error (invalid/private collaborator username) to a friendlier message
  in InstagramPublishException. I didn't add a guessed error_subcode
  entry - the existing fallback already surfaces Meta's own
  error_user_msg when present, and I'd rather not fabricate an
  unconfirmed code mapping (this table is built from Meta's official
  error-code docs, not guesses).
• Status-check endpoint (invite Accepted/Pending/Declined): explicitly
  called out in the issue as a v2 follow-up, not needed here.
• Docs site (docs.trypost.it): out of scope for this repo.

Test plan

• tests/Feature/Services/Social/InstagramPublisherTest.php - 5 new tests: collaborators on a reel container, on a single-image container, omitted when unset, never sent on a story, and present only on the carousel's parent container (not child items)
• tests/Unit/PostPlatformMetaRulesTest.php, tests/Feature/Api/PostApiPlatformMetaTest.php, tests/Feature/Mcp/PostPlatformMetaToolTest.php - rule presence, cross-platform persistence (API), and MCP create-post coverage, plus a max-3 rejection test in each entry point
• php artisan test --compact tests/Unit/PostPlatformMetaRulesTest.php tests/Feature/Api/PostApiPlatformMetaTest.php tests/Feature/Mcp/PostPlatformMetaToolTest.php tests/Feature/Services/Social/InstagramPublisherTest.php - 105 passed
• vendor/bin/pint --dirty --format agent - passed

Addresses #213 (validation + publisher; composer UI and error-message mapping left as follow-ups per above)

[Copilot]

Pull request overview

Adds support for Instagram “collaborators” (up to 3 usernames) by accepting the meta field across entry points and passing it through to the correct Instagram media container creation call (Reels, single images, and carousel parent containers only).

Changes:

• Added platforms.*.meta.collaborators validation to PostPlatformMetaRules (array max 3; each username max 30 chars).
• Updated InstagramPublisher to attach JSON-encoded collaborators on the publishable container (single image / reel / carousel parent).
• Added/updated API, MCP, unit, and service tests to ensure persistence and correct request payload behavior.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
app/Support/PostPlatformMetaRules.php	Adds validation rules for Instagram meta.collaborators.
app/Services/Social/InstagramPublisher.php	Adds withCollaborators() helper and applies it to the appropriate container creation flows.
tests/Unit/PostPlatformMetaRulesTest.php	Ensures the shared meta rules include the new collaborators key.
tests/Feature/Services/Social/InstagramPublisherTest.php	Adds coverage for collaborators being included/omitted and carousel-parent-only behavior.
tests/Feature/Api/PostApiPlatformMetaTest.php	Verifies API persistence and validates max-3 rejection.
tests/Feature/Mcp/PostPlatformMetaToolTest.php	Verifies MCP create-post persistence and validates max-3 rejection.

Suppressed comments (1)

tests/Feature/Services/Social/InstagramPublisherTest.php:257

• This assertion may match the GET polling request to the container (which will never have collaborators), so the test could still pass even if the story container creation request accidentally included collaborators. Filter down to the POST /{ig-id}/media container creation request to avoid false positives.

    Http::assertSent(function ($request) {
        return ! str_contains($request->url(), 'media_publish')
            && ! isset($request['collaborators']);
    });

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[HafizMMoaz]

Good catch - fixed both. Scoped the assertions to the actual /ig_123456789/media container-creation request (excluding media_publish), so they no longer trivially pass against the status-check GET request that also lacks collaborators.

[paulocastellano]

@HafizMMoaz i'm closing this pull request in favor of #283

It's already done for code review, test, feel free to test it.

I'm planing to merge it today/tomorrow.