[Rules] Add rules for requiring custom files from client (#4561)

* rules for enabling requiring custom files

* shorten default

* variable name

* check account status for enforcing client key

* rule for custom files admin level

---------

Co-authored-by: Paul Johnson <Paul@pjohnsomac-6366.digi.box>

world/client.cpp

@@ -541,6 +541,17 @@ bool Client::HandleSendLoginInfoPacket(const EQApplicationPacket *app)
 					skip_char_info = true;
 				}
 			}
+			const auto& custom_files_key = RuleS(World, CustomFilesKey);
+			if (!skip_char_info && !custom_files_key.empty() && cle->Admin() < RuleI(World, CustomFilesAdminLevel)) {
+				// Modified clients can utilize this unused block in login_info to send custom payloads on login
+				// which indicates they are using custom client files with the correct version, based on key payload.
+				const auto client_key = std::string(reinterpret_cast<char*>(login_info->unknown064));
+				if (custom_files_key != client_key) {
+					std::string message = fmt::format("Missing Files [{}]", RuleS(World, CustomFilesUrl) );
+					SendUnsupportedClientPacket(message);
+					skip_char_info = true;
+				}
+			}
 
 			if (!skip_char_info) {
 				SendExpansionInfo();