Add SCIM 2.0 configuration and setup documentation

[dieu-bis]

Summary

This PR adds documentation for the SCIM 2.0 feature in Open WebUI, covering environment configuration and setup instructions for identity providers.

Changes

Environment Configuration

• Added SCIM environment variables (SCIM_ENABLED and SCIM_TOKEN) to /docs/getting-started/env-configuration.md
• Documented that both are PersistentConfig variables
• Included security recommendations for token generation

SCIM Feature Documentation

• Created comprehensive SCIM documentation at /docs/features/scim.mdx
• Covered:
  • SCIM overview and benefits
  • Configuration via environment variables
  • API endpoint details (base URL and authentication)
  • Setup guides for Okta, Azure AD, and Google Workspace
  • Supported operations and attributes
  • Filtering capabilities
  • Troubleshooting common issues
  • Security considerations
  • Integration with SSO

Key Information Documented

• SCIM Base URL: <openwebui-base-url>/api/v1/scim/v2/
• Authentication: Bearer Token format Bearer <your-token>
• Supported Operations: Full CRUD for users and groups
• Identity Provider Examples: Step-by-step setup for major providers

Feature PR

15694

This documentation enables administrators to properly configure SCIM for automated user provisioning from their identity management systems.

This PR description focuses specifically on the documentation additions rather than the implementation details.