Removing all "any" from back.

To do this, I used generic-type-guard package which generates both an interface AND a valid type guard from code.
With this, we are 100% sure that the messages we receive are validated at runtime!
The client cannot pass us an object that is invalid! \o/

back/src/Model/Websocket/WebRtcSignalMessage.ts

@@ -0,0 +1,10 @@
+import * as tg from "generic-type-guard";
+
+export const isWebRtcSignalMessageInterface =
+    new tg.IsInterface().withProperties({
+        userId: tg.isString,
+        receiverId: tg.isString,
+        roomId: tg.isString,
+        signal: tg.isUnknown
+    }).get();
+export type WebRtcSignalMessageInterface = tg.GuardedType<typeof isWebRtcSignalMessageInterface>;