feat(AppConfig): iterate how apps are managed

- auth clients are always shared, cannot be disabled
- custom connections are enabled by default, can be disabled
- any existing connections can be reconnected regardless of its AppConfig or AppAuthClient states

packages/backend/src/models/__snapshots__/app-config.test.js.snap

@@ -3,17 +3,9 @@
 exports[`AppConfig model > jsonSchema should have correct validations 1`] = `
 {
   "properties": {
-    "connectionAllowed": {
-      "default": false,
-      "type": "boolean",
-    },
     "createdAt": {
       "type": "string",
     },
-    "customConnectionAllowed": {
-      "default": false,
-      "type": "boolean",
-    },
     "disabled": {
       "default": false,
       "type": "boolean",
@@ -25,13 +17,13 @@ exports[`AppConfig model > jsonSchema should have correct validations 1`] = `
     "key": {
       "type": "string",
     },
-    "shared": {
-      "default": false,
-      "type": "boolean",
-    },
     "updatedAt": {
       "type": "string",
     },
+    "useOnlyPredefinedAuthClients": {
+      "default": false,
+      "type": "boolean",
+    },
   },
   "required": [
     "key",