Is it possible to use a discord text channel as a console. Like you can enter commands and also you can see the outputs.

Yes, but this is more Discord bot/app functionality than a rust server plugin. Using node.js, for instance, you can utilize the webrconjs package to facilitate RCON commands to your rust server and receive the console responses back and relay them into the instantiating Discord TextChannel. This functionality would have to be accompanied by other measures including permissions and connection audits.

But is it possible to make this as a plugin for rust?

A plugin is not necessary to do what you are wanting to do... the functionality is all external to the server itself. All your Rust server is doing in your requested scenario is processing console commands as it would via any RCON tool or normal console input. No plugin is necessary to accomplish this default behavior. You're asking for a way to facilitate this exchange externally through another service. Thus, the tool you need is related to Discord, not Rust. 

Yes i know there are RCON tools and i use them, but i want to control my server through discord and maybe just assign my friends a role and make them be able to control it too + Control via my phone. Anyway turns out there was a plugin that does this after all.
https://umod.org/plugins/discord-commands

I completely understand what you want to do and outlined how to do it and was simply stating that you don't need a Rust plugin to accomplish it. However, my point still stands: the "Discord Commands" plugin you linked utilizes a Discord bot to achieve what you want (the Rust plugin itself only acts as an additional in-game permissions qualifier), which is exactly what I told you that you needed from the start: a Discord bot or app to act as a conduit to the Rust server for RCON commands. This plugin, or any Rust plugin, is not necessary to achieve that functionality. This plugin joins a bot to your Discord server that transmits the commands to your Rust server. You can do the exact same thing, with less overhead, without this plugin.

You could use this RustyWatcher