✨ Adds MariaDB image with direct LDAP PAM authentication

- Introduced a new Containerfile to build a MariaDB image with direct LDAP PAM support.
- Implemented a custom PAM module (`pam_ldap_direct.so`) built from the PADL source to avoid dependencies on `libpam-ldap` and `nslcd`.
- Updated the entrypoint script to dynamically generate the PAM configuration file (`/etc/pam_ldap.conf`) based on environment variables.
- Added a README.md to document the image usage, configuration, and build process.
- Created a test suite to validate the image build and entrypoint behavior, ensuring proper handling of environment variables and configuration generation.
- Configured health checks and ensured the stock MariaDB entrypoint and lifecycle are preserved.

database/mariadb/pam.d/mariadb

@@ -1,6 +1,2 @@
-# PAM service for MariaDB auth_pam logins (accounts created IDENTIFIED VIA pam
-# USING 'mariadb'). Authenticate + authorize against Active Directory through
-# the daemonless pam_ldap module; its connection settings live in
-# /etc/pam_ldap.conf, rendered at container start from the environment.
-auth     required   pam_ldap.so
-account  required   pam_ldap.so
+auth     required   /usr/local/lib/security/pam_ldap_direct.so
+account  required   /usr/local/lib/security/pam_ldap_direct.so