doctor: print [INFO] for checkTrustedUser()

This adds a new function checkInfo which prints with no consequence to
the exit code, we then use it to print whether the Nix client is a
trusted-user on the store

src/nix/doctor.cc

@@ -33,6 +33,10 @@ bool checkFail(const std::string & msg) {
     return false;
 }
 
+void checkInfo(const std::string & msg) {
+    notice(ANSI_BLUE "[INFO] " ANSI_NORMAL + msg);
+}
+
 }
 
 struct CmdDoctor : StoreCommand
@@ -55,6 +59,7 @@ struct CmdDoctor : StoreCommand
             success &= checkProfileRoots(store);
         }
         success &= checkStoreProtocol(store->getProtocol());
+        checkTrustedUser(store);
 
         if (!success)
             throw Exit(2);
@@ -130,6 +135,15 @@ struct CmdDoctor : StoreCommand
 
         return checkPass("Client protocol matches store protocol.");
     }
+
+    void checkTrustedUser(ref<Store> store)
+    {
+        bool trusted = store->checkTrustedUser();
+        if (trusted)
+            checkInfo("You are a trusted-user on store uri: " + store->getUri());
+        if (!trusted)
+            checkInfo("You are not a trusted-user on store uri: " + store->getUri());
+    }
 };
 
 static auto rCmdDoctor = registerCommand<CmdDoctor>("doctor");