Add: LoginParser to check for required parameter and construct LoginRequest

src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/app/commands/login/LoginParser.java

@@ -0,0 +1,14 @@
+package ch.unibas.dmi.dbis.cs108.casono.server.app.commands.login;
+
+import ch.unibas.dmi.dbis.cs108.casono.server.network.command.parsing.CommandParser;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.protocol.request.PrimitiveRequest;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.protocol.request.accessor.RequestParameterAccessor;
+
+public class LoginParser implements CommandParser<LoginRequest> {
+    @Override
+    public LoginRequest parse(PrimitiveRequest primitiveRequest) {
+        RequestParameterAccessor accessor =
+                new RequestParameterAccessor(primitiveRequest.parameters());
+        return new LoginRequest(primitiveRequest.context(), accessor.require("USERNAME"));
+    }
+}