fix(recovery): Fix installation recovery current step resolving

- Refactor the nested if-pyramid
- Replace the DnsProviderType check with a simple check for a token string, since we receive DnsProviderType from the server and the user has no actions in it
- Make sure the server selection prompt isn't skipped before asking for a DNS token
- Resolve: #395

lib/logic/cubit/server_installation/server_installation_repository.dart

@@ -156,19 +156,22 @@ class ServerInstallationRepository {
     final ServerDomain serverDomain,
     final ServerHostingDetails? serverDetails,
   ) {
-    if (serverDetails != null) {
+    if (serverDetails == null) {
-      if (serverProviderToken != null) {
+      return RecoveryStep.selecting;
-        if (serverDetails.provider != ServerProviderType.unknown) {
+    }
-          if (serverDomain.provider != DnsProviderType.unknown) {
+
-            return RecoveryStep.backblazeToken;
+    if (serverProviderToken == null) {
-          }
-          return RecoveryStep.dnsProviderToken;
-        }
-        return RecoveryStep.serverSelection;
-      }
       return RecoveryStep.serverProviderToken;
     }
-    return RecoveryStep.selecting;
+
+    /// We don't write anything to the database after .serverSelection
+    /// step, therefore we have to re-ask it again before prompting for
+    /// DNS token, if it wasn't provided yet.
+    if (dnsProviderToken == null) {
+      return RecoveryStep.serverSelection;
+    }
+
+    return RecoveryStep.backblazeToken;
   }
 
   void clearAppConfig() {