init server_name to be the sld

Dockerfile

@@ -21,7 +21,7 @@ ENV PATH="$VIRTUAL_ENV/bin:$PATH"
 # lxml - required for previews
 RUN pip install --upgrade pip && \
     pip install --upgrade setuptools && \
-    pip install matrix-synapse==${VERSION} psycopg2-binary python-ldap matrix-synapse-ldap3 lxml
+    pip install matrix-synapse==${VERSION} psycopg2-binary python-ldap matrix-synapse-ldap3 lxml publicsuffix2
 
 RUN curl -sL https://github.com/mikefarah/yq/releases/download/3.2.1/yq_linux_amd64 -o /usr/bin/yq && \
     chmod +x /usr/bin/yq