Merge #14451: Add BIP70 deprecation warning and allow building GUI without BIP70 support

48439b3c10 Don't link SSL_LIBS with GUI unless BIP70 is enabled (James Hilliard)
fbb643d2a5 Add BIP70 deprecation warning (James Hilliard)
38b98507cd qt: cleanup: Move BIP70 functions together in paymentserver (Wladimir J. van der Laan)
9dcf6c0dfe build: Add --disable-bip70 configure option (Wladimir J. van der Laan)

Pull request description:

  This is based off of #11622 and adds a deprecation warning when a BIP70 URL is used.

  Rational:

  - BIP70 increases attack surface in multiple ways and is difficult for third party wallets to implement in a secure manner
  - Very few merchants use the standard BIP70 variant supported by Bitcoin Core
  - The one major payment processor that doesn't support BIP21 and currently uses a customized non-standard version of BIP70 has indicated that "Unfortunately the original BIP70 is not useful for us."

Tree-SHA512: 1e16ee8d2cdac9499f751ee7b50d058278150f9e38a87a47ddb5105dd0353cdedabe462903f54ead6209b249b249fe5e6a10d29631531be27400f2f69c25b9b9

src/qt/bitcoin.cpp

@@ -439,8 +439,10 @@ void BitcoinApplication::addWallet(WalletModel* walletModel)
         window->setCurrentWallet(walletModel->getWalletName());
     }
 
+#ifdef ENABLE_BIP70
     connect(walletModel, &WalletModel::coinsSent,
         paymentServer, &PaymentServer::fetchPaymentACK);
+#endif
     connect(walletModel, &WalletModel::unload, this, &BitcoinApplication::removeWallet);
 
     m_wallet_models.push_back(walletModel);
@@ -467,7 +469,9 @@ void BitcoinApplication::initializeResult(bool success)
         // Log this only after AppInitMain finishes, as then logging setup is guaranteed complete
         qWarning() << "Platform customization:" << platformStyle->getName();
 #ifdef ENABLE_WALLET
+#ifdef ENABLE_BIP70
         PaymentServer::LoadRootCAs();
+#endif
         paymentServer->setOptionsModel(optionsModel);
 #endif
 
@@ -536,7 +540,7 @@ WId BitcoinApplication::getMainWinId() const
 
 static void SetupUIArgs()
 {
-#ifdef ENABLE_WALLET
+#if defined(ENABLE_WALLET) && defined(ENABLE_BIP70)
     gArgs.AddArg("-allowselfsignedrootcertificates", strprintf("Allow self signed root certificates (default: %u)", DEFAULT_SELFSIGNED_ROOTCERTS), true, OptionsCategory::GUI);
 #endif
     gArgs.AddArg("-choosedatadir", strprintf("Choose data directory on startup (default: %u)", DEFAULT_CHOOSE_DATADIR), false, OptionsCategory::GUI);