Added GSSAPI Authentication.

Dockerfile

@@ -5,6 +5,7 @@ RUN apt-get update && \
     DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
         slapd \
         ldap-utils \
+        libsasl2-modules-gssapi-mit \
         python3-jinja2 \
         python3-ldap3 && \
     rm -rf /var/lib/apt/lists/*