docs(airflow): Document the need for installed packages (#918)

* docs(airflow): Document the need for installed packages

* fix compilation because of comments

* Save 2 layers :)

* revert layer optimization

airflow/Dockerfile

@@ -99,25 +99,28 @@ ENV AIRFLOW_USER_HOME_DIR=/stackable
 ENV PATH=$PATH:/bin:$HOME/app/bin
 ENV AIRFLOW_HOME=$HOME/airflow
 
-# Update image and install python
-RUN <<EOF
-microdnf update
-microdnf install \
-  ca-certificates \
-  cyrus-sasl \
-  git \
-  libpq \
-  openldap \
-  openldap-clients \
-  openssh-clients \
-  openssl-libs \
-  openssl-pkcs11 \
-  python${PYTHON} \
-  socat \
-  unixODBC
-microdnf clean all
-rm -rf /var/cache/yum
-
+# Update image and install needed packages
+RUN microdnf update && \
+    microdnf install \
+        ca-certificates \
+        cyrus-sasl \
+        # Needed for the gitsync functionality
+        git \
+        libpq \
+        # Needed for authentication of clients against LDAP servers
+        openldap \
+        openldap-clients \
+        # We need the openssh libs for the gitsync functionality (the clone target could be e.g. git@github.com:org/repo.git)
+        openssh-clients \
+        openssl-libs \
+        openssl-pkcs11 \
+        # Airflow needs Python
+        python${PYTHON} \
+        socat \
+        unixODBC && \
+    microdnf clean all && \
+    rm -rf /var/cache/yum && \
+bash <<EOF
 # Get the correct `tini` binary for our architecture.
 # It is used as an init alternative in the entrypoint
 curl -o /usr/bin/tini "https://repo.stackable.tech/repository/packages/tini/tini-${TINI}-${TARGETARCH}"