ews: unconditionally emit all OOF XML tags upon GetUserOofSettingsRequest

Outlook 2019 MSO (v2506 Build 16.0.18925.20076) is prone to reliable
crashing when attempting to save OOF settings after miniscule
changes. Not all OL versions exhibit the behavior, but if one
{version, mailbox} combination does crash, it does quite reliably so.

It appears that the crash is averted when *all* OOF XML tags are
present at all times, even if OOF is disabled. This suggests that OL
(1.) violates specification MS-OXWOOF v16 §2.2.4.2 which clearly
permits absence of some tags, (2.) has a nullptr deference somewhere,
akin to:

```
// on GetUserOofSettings:
this->starttime = xmlFindNode(tree, "StartTime");

// on SetUserOofSettings:
this->starttime->set("2025-12-01 00:00:00");
```

References: GXL-605, DESK-3609, DESK-3614, DESK-3666

Author: jengelh

doc/outlook_oof_spec.rst

@@ -28,10 +28,10 @@ Editing the FAI messages' ``PR_BODY`` will not change the automatic reply body.
 Changing e.g. the ``PR_MESSAGE_CLASS`` however will make Exchange stop sending
 the reply, even if it is changed back afterwards.
 
-Internet search suggests that OOF is set using the EWS API instead.
+OOF is get/set by Outlook using the EWS API instead.
 
-MAPI only gets gratitious copies, and only of certain information, making it
-practically useless.
+MAPI only gets gratitious copies, and only of certain information, making
+those copies practically useless.
 
 
 OOF levels

exch/ews/requests.cpp

@@ -944,10 +944,10 @@ void process(mGetUserOofSettingsRequest&& request, XMLElement* response, const E
 	std::string maildir = ctx.get_maildir(request.Mailbox);
 	string configPath = maildir+"/config/autoreply.cfg";
 	auto configFile = config_file_init(configPath.c_str(), oof_defaults);
-	if (configFile) {
-		auto oof_state          = configFile->get_ll("oof_state");
-		auto allow_external_oof = configFile->get_ll("allow_external_oof");
-		auto external_audience  = configFile->get_ll("external_audience");
+	unsigned int oof_state  = configFile != nullptr ? configFile->get_ll("oof_state") : 0;
+	bool allow_external_oof = configFile != nullptr ? configFile->get_ll("allow_external_oof") : false;
+	bool external_audience  = configFile != nullptr ? configFile->get_ll("external_audience") : false;
+	if (true) {
 		switch(oof_state) {
 		case 1:
 			data.OofSettings->OofState = "Enabled"; break;
@@ -966,15 +966,20 @@ void process(mGetUserOofSettingsRequest&& request, XMLElement* response, const E
 			tDuration& Duration = data.OofSettings->Duration.emplace();
 			Duration.StartTime = clock::from_time_t(strtoll(start_time, nullptr, 0));
 			Duration.EndTime = clock::from_time_t(strtoll(end_time, nullptr, 0));
+		} else {
+			auto &dur = data.OofSettings->Duration.emplace();
+			dur.StartTime = clock::now();
+			dur.EndTime = dur.StartTime + std::chrono::days(1);
 		}
 		optional<string> reply = readMessageBody(maildir+"/config/internal-reply");
 		if (reply)
 			data.OofSettings->InternalReply.emplace(std::move(reply));
+		else
+			data.OofSettings->InternalReply.emplace(std::string{});
 		if ((reply = readMessageBody(maildir+"/config/external-reply")))
 			data.OofSettings->ExternalReply.emplace(std::move(reply));
-	} else {
-		data.OofSettings->OofState = "Disabled";
-		data.OofSettings->ExternalAudience = "None";
+		else
+			data.OofSettings->ExternalReply.emplace(std::string{});
 	}
 
 	//Finalize response