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/package.json

@@ -16,7 +16,8 @@
     "type": "git",
     "url": "git+https://github.com/thecodingmachine/workadventure.git"
   },
-  "contributors": [{
+  "contributors": [
+    {
       "name": "Grégoire Parant",
       "email": "g.parant@thecodingmachine.com"
     },
@@ -27,7 +28,8 @@
     {
       "name": "Arthmaël Poly",
       "email": "a.poly@thecodingmachine.com"
-    }],
+    }
+  ],
   "license": "SEE LICENSE IN LICENSE.txt",
   "bugs": {
     "url": "https://github.com/thecodingmachine/workadventure/issues"
@@ -41,6 +43,7 @@
     "@types/uuidv4": "^5.0.0",
     "body-parser": "^1.19.0",
     "express": "^4.17.1",
+    "generic-type-guard": "^3.2.0",
     "http-status-codes": "^1.4.0",
     "jsonwebtoken": "^8.5.1",
     "prom-client": "^12.0.0",