start-mailserver.sh split (#1820)

* splitting start-mailserver.sh

* refactoring part 2

* refactored setup-stack.sh
* stzarted adjusting target/bin/*.sh to use new usage format

* corrected lowercase-uppercase test error

* better handling of .bashrc variable export

* linting tests and fix for default assignements

* last stylistic changes and rebase

target/scripts/startup/check-stack.sh

@@ -0,0 +1,31 @@
+#! /bin/bash
+
+function check
+{
+  _notify 'tasklog' 'Checking configuration'
+  for FUNC in "${FUNCS_CHECK[@]}"
+  do
+    ${FUNC} || _defunc
+  done
+}
+
+function _check_hostname
+{
+  _notify 'task' 'Checking that hostname/domainname is provided or overridden'
+
+  if [[ -n ${OVERRIDE_HOSTNAME} ]]
+  then
+    export HOSTNAME=${OVERRIDE_HOSTNAME}
+    export DOMAINNAME="${HOSTNAME#*.}"
+  fi
+
+  _notify 'inf' "Domain has been set to ${DOMAINNAME}"
+  _notify 'inf' "Hostname has been set to ${HOSTNAME}"
+
+  if ! grep -q -E '^(\S+[.]\S+)$' <<< "${HOSTNAME}"
+  then
+    _notify 'err' 'Setting hostname/domainname is required'
+    kill "$(< /var/run/supervisord.pid)"
+    return 1
+  fi
+}