feat(frontier): add optional relation field to RemovePlatformUserRequest

[rohilsurana]

What

Adds an optional relation field (field number 3) to RemovePlatformUserRequest in raystack/frontier/v1beta1/admin.proto.

message RemovePlatformUserRequest {
  string user_id = 1;
  string serviceuser_id = 2;

  // relation scopes the removal to a single platform relation (admin or member).
  // When empty, all platform relations of the principal are removed.
  string relation = 3;
}

Unlike the sibling AddPlatformUserRequest.relation, this field is optional (not REQUIRED): an empty relation must preserve today's behavior of removing the principal entirely.

Why

This unblocks relation-selective platform-user removal in Frontier. Today Frontier's RemovePlatformUser strips both the admin (superuser) and member (check) platform relations because the request has no relation field, so there is no way to demote an admin down to member or remove just one relation via the API.

Adding this optional field lets callers target a single relation (admin or member) while the empty default stays 100% backward compatible. It is a prerequisite for a declarative platform-user reconciler in Frontier, which must converge (principal, relation) pairs precisely. Frontier regenerates its Go stubs from this repo, so the field must land here first.

Backward compatibility

• New optional proto3 scalar field, additive only. Wire-compatible.
• buf lint and buf format pass.

[github-actions]

The latest Buf updates on your PR. Results from workflow Validate / validate (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	⏩ skipped	✅ passed	✅ passed	Jun 29, 2026, 11:54 AM

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 6ce44b9e-4c1b-4dd6-9bde-69813766d454

📥 Commits

Reviewing files that changed from the base of the PR and between 795c70f and df63535.

📒 Files selected for processing (1)

• raystack/frontier/v1beta1/admin.proto

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📝 Walkthrough

Walkthrough

In admin.proto, the RemovePlatformUserRequest message gains a new optional string relation = 3 field. Documentation on the field states that when provided, the removal is scoped to that specific platform relation type; when left empty, all platform relations for the principal are removed.

Possibly related issues

• RemovePlatformUser is not relation-selective (asymmetric with AddPlatformUser) frontier#1710: The added relation field in RemovePlatformUserRequest directly enables relation-selective platform user removal, which aligns with the gap described in this issue.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: adding an optional relation field to RemovePlatformUserRequest.
Description check	✅ Passed	The description is directly related to the changeset and explains the new field, behavior, and motivation.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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