There is a demo plugin that allows the devices to get the server's time. The current date and time is not very convenient for parsing in a microcontroller, and I would like to change the response to a Unix timestamp.
In the documentation it is stated that this is possible, but it not very clear how. Is there a guide on how can I configure the plug-in?
Also, getting the server's time is very important for non-ntp enabled devices (or when inside a VPN, without access to an NTP server). Are there any plans to integrate this functionality to the core of Thingsboard, or it will remain a demo plug-in?
The plugin you talk about is the part of the core now. You can edit plugin output format in the configuration of the plugin. Go to Plugins->your plugin->edit mode