updates for testnet4 (#1874)

docs/FAQ/FAQ-UseWasabi.md

@@ -874,12 +874,11 @@ Now if even that would fail, then we can start thinking about lowering the requi
 
 ### I'd like to experience coinjoin but I'm not comfortable using real Bitcoin. What can I do?
 
-You can try to make a coinjoin via Wasabi on the Bitcoin [TestNet](/using-wasabi/Testnet.md) (an alternative Bitcoin network, to be used for testing).
-Go to `Settings` > `Bitcoin` and change the network to `TestNet`.
+You can try to make a coinjoin via Wasabi on the Bitcoin [TestNet4](/using-wasabi/Testnet.md) (an alternative Bitcoin network, to be used for testing).
+Go to `Settings` > `Bitcoin` and change the network to `TestNet4`.
 Then restart your Wasabi and create a new wallet, this is needed because Wasabi differentiates between "Main wallets" and "TestNet wallets".
 This wallet will synchronize for the TestNet, and generate TestNet addresses.
-You can get tBTC from faucets like:
-[coinfaucet.eu/en/btc-testnet](https://coinfaucet.eu/en/btc-testnet/) or [bitcoinfaucet.uo1.net](https://bitcoinfaucet.uo1.net/)
+You can get tBTC from faucets like [this one](https://faucet.testnet4.dev/) or [https://coinfaucet.eu/en/btc-testnet4/](https://coinfaucet.eu/en/btc-testnet4/).
 
 ### Does Wasabi have to stay on during coinjoin?
 

docs/using-wasabi/Testnet.md

@@ -15,6 +15,8 @@ The Bitcoin testnet is a network that behaves almost exactly the same as the Bit
 The major difference is that the bitcoin on the testnet do not have any economical value, they should not be used to buy or sell goods and services.
 This makes the network very useful for testing software and features, because there is no risk of losing precious "real" bitcoin from the main network.
 
+Wasabi uses testnet4.
+
 :::tip Don't loose your bitcoin
 When testing cutting edge software like Wasabi, use testnet to ensure that your mistakes don't cost you money!
 :::
@@ -25,16 +27,16 @@ First, open your Wasabi Wallet and click the `Settings` button in the bottom lef
 
 ![Settings button](/SettingsButton.png "Settings button")
 
-Select the `Bitcoin` tab, click on the `Network` dropdown and select `TestNet`.
+Select the `Bitcoin` tab, click on the `Network` dropdown and select `TestNet4`.
 
 ![Settings Network Dropdown](/SettingsNetwork.png "Settings Network Dropdown")
 
 Restart Wasabi to activate the change.
-After the restart, you should see the `TestNet` indicator in the top right corner of the wallet.
+After the restart, you should see the `TestNet4` indicator in the top right corner of the wallet.
 
 ![Bitcoin testnet network activated in Wasabi Wallet](/TestNetIndicator.png "Bitcoin testnet network activated in Wasabi Wallet")
 
-When Wasabi is started in testnet, it will fetch testnet [BIP 158 block filters](https://github.com/bitcoin/bips/blob/master/bip-0158.mediawiki) from the backend.
+When Wasabi is started in testnet, it will fetch testnet4 block filters from the backend.
 For the first start, this may take a couple of minutes.
 
 After the testing, set the settings back to mainnet, and close Wasabi.
@@ -58,10 +60,12 @@ You can [generate a receive address](/using-wasabi/Receive.md) the same way as o
 Notice that testnet SegWit addresses start with `tb1q...`, and not with `bc1q...` as mainnet addresses.
 
 Because testnet bitcoin don't have economical value, they are gifted by different sources.
-There are [faucets](https://en.bitcoin.it/wiki/Testnet#Faucets) like [this one](https://coinfaucet.eu/en/btc-testnet/) or [bitcoinfaucet.uo1.net](https://bitcoinfaucet.uo1.net/) that give a certain amount of testnet bitcoin per time period.
+There are faucets like [this one](https://faucet.testnet4.dev/) or [https://coinfaucet.eu/en/btc-testnet4/](https://coinfaucet.eu/en/btc-testnet4/).
 You may also ask other developers if they have a couple of spare testnet coins available.
 
 ## Coinjoin on testnet
 
-[CoinJoin](/using-wasabi/CoinJoin.md) on testnet is as easy as on mainnet.
-Usually there are other testers doing a coinjoin, but if you are the only one at the moment, then load two wallets and start coinjoining in both of them.
+[CoinJoin](/using-wasabi/CoinJoin.md) on testnet can be as easy as on mainnet.
+However, not all mainnet coordinators also run a testnet coordinator.
+The testnet coordinator that the Wasabi team uses can be used for testing: `https://api.wasabiwallet.co/`.
+Sometimes there are other testers doing a coinjoin, but if you are the only one at the moment, then load two wallets and start coinjoining in both of them or ask someone to join you.