MCP server install API ignores target user for personal installs

[priyanshu0x]

Problem

The Terraform provider needs to support the real-world admin workflow of pre-provisioning a personal MCP server installation for another user. The current platform API shape appears to support this (InsertMcpServerSchema has userId, and McpServerModel.create() uses userId to assign the personal MCP server), but the install route overwrites the requested target user with the authenticated request user.

This means an admin cannot install an MCP server on behalf of another user. Any provider-side user_id field would be ignored by the backend and would either create the install for the API key owner or return an existing personal install for the API key owner.

Verified against latest upstream/main at 6744195f9.

Evidence

In platform/backend/src/routes/mcp-server.ts, POST /api/mcp_server currently overwrites target ownership:

// Set owner_id and userId to current user
serverData.ownerId = user.id;
serverData.userId = user.id;

The same route also checks duplicate personal installs against the authenticated user instead of a requested target user:

if (serverData.scope === "personal") {
  const existingPersonal = existingServers.find(
    (s) => s.scope === "personal" && s.ownerId === user.id,
  );

But platform/backend/src/types/mcp-server.ts exposes the intended request field:

userId: z.string().optional(), // For personal auth

And platform/backend/src/models/mcp-server.ts already uses userId for the personal install semantics:

const { userId, ...serverData } = server;
// ... construct local name with ownerId: userId
if (userId) {
  await McpServerUserModel.assignUserToMcpServer(createdServer.id, userId);
}

Expected behavior

For scope = "personal":

• If the request omits userId, keep current behavior: install for the authenticated user.
• If the request includes userId, allow users with sufficient permissions to install for that target user.
• Store ownerId and the mcp_server_user assignment for the target user, not the authenticated API user.
• Duplicate detection should key on the effective target user, not always user.id.
• Existing current-user personal install behavior remains unchanged.

Permission expectation

Suggested policy: only users with mcpServerInstallation:admin can install a personal MCP server for another user. Regular users should still only install for themselves.

Acceptance criteria

• POST /api/mcp_server with scope: "personal" and userId: <other-user-id> creates or returns the personal install for <other-user-id> when caller has admin permission.
• The response includes ownerId = <other-user-id> and users / userDetails include <other-user-id>.
• Duplicate personal install detection uses <other-user-id>.
• A non-admin caller gets a 403 when targeting another user.
• Terraform provider can safely add archestra_mcp_server_installation.user_id without a backend-ignore guard firing.

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