Discussion and Questions on Local/AD/LDAP Authentication

**Is your feature request related to a problem? Please describe.**

Currently, git-proxy supports three authentication mechanisms: local, Active Directory (AD), and OpenID Connect (OIDC). However, there are gaps that make it difficult for small-scale deployments and trial users:

1. **Local authentication** has limited functionality—users can be added via API/CLI (as of late last year; #981), but there's no way to delete users and no WebUI is provided.
2. **AD authentication** is complex and unfamiliar to most developers, requiring significant effort to set up for initial users.

These limitations create friction for first-time users trying to evaluate or deploy git-proxy in small environments.

**Describe the solution you'd like**

Add LDAP authentication support to git-proxy, with a focus on lightweight LDAP solutions suitable for small-scale environments. Specifically:

1. Provide a docker-compose example configuration using a lightweight LDAP server (e.g., [lldap](https://github.com/lldap/lldap)) with an integrated GUI.
2. This would allow users to quickly test LDAP authentication without the complexity of full Active Directory.
3. Similar to how MongoDB is included in the existing docker-compose setup, a functional LDAP server in docker-compose would lower the barrier to entry for new users.

**Describe alternatives you've considered**

1. **Enhance local authentication**: Add user deletion capability and implement a WebUI.
2. **Improve AD documentation/examples**: Provide a working AD server in docker-compose—I've successfully integrated OpenLDAP and phpLDAPadmin (WebUI) with git-proxy, and if you think it would be helpful, I'll submit a PR with a complete example including docker-compose and LDIF configuration.

**Additional context**

Is my understanding correct? I'd appreciate your feedback and thoughts on this.