✨ 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/.gitattributes

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+Containerfile text eol=lf
+docker-entrypoint.sh text eol=lf
+pam.d/mariadb text eol=lf
+conf.d/*.cnf text eol=lf
+tests/*.py text eol=lf
+README.md text eol=lf
+.gitattributes text eol=lf