Allow creating users via API without invitation (service users)

[stasvangus]

Dokploy has a solid API for automating infrastructure and application provisioning, but currently user creation is invitation-only. This creates a hard blocker for fully automated, multi-tenant integrations (e.g. WHMCS, SaaS platforms, internal PaaS offerings).

Problem

1. For API-driven platforms, invitations introduce human interaction into flows that must be fully automated:
2. Cannot silently provision isolated tenants
3. Cannot create per-organization service users
4. Cannot generate per-tenant API keys programmatically
5. Forces operators to reuse a global admin API key, increasing blast radius and security risk

This makes Dokploy difficult to use as a backend for hosting providers and SaaS platforms.

Proposed solution
Introduce API-based user creation without invitations, specifically for service / automation users.

Example
POST /api/users { "email": "service-client-123@internal", "name": "Client 123 Service User", "organization_id": "org_xxx", "role": "developer", "type": "service", "skip_invite": true }