EWS GetFolder: t:FolderClass missing in AllProperties shape response, breaks Outlook for Mac shared calendars

## Description `GetFolder` with `<t:BaseShape>AllProperties</t:BaseShape>` does not include `<t:FolderClass>` in the response, even though `AllProperties` should return all first-class properties per the EWS schema. The value is stored correctly (explicit `folder:FolderClass` in `AdditionalProperties` returns it), but `AllProperties` silently omits it. This breaks shared calendar display in Outlook for Mac: it fetches the shared folder via `AllProperties`, receives a `<t:CalendarFolder>` without `FolderClass`, and does not recognize it as a calendar. Result: the shared folder is added to the account but `Calendars in Account: 0` and it never appears in the calendar sidebar. ## Environment - gromox 2.45.0.b785b87-lp156.4.1.x86_64 (openSUSE Leap 15.6) - Client: Outlook for Mac 2024, Build 16.108.26041915, Office LTSC Standard 2021 ## Reproduction ### Request with AllProperties shape ```xml <m:GetFolder> <m:FolderShape><t:BaseShape>AllProperties</t:BaseShape></m:FolderShape> <m:FolderIds> <t:DistinguishedFolderId Id="calendar"> <t:Mailbox><t:EmailAddress>someuser@example.com</t:EmailAddress></t:Mailbox> </t:DistinguishedFolderId> </m:FolderIds> </m:GetFolder> ``` ### Observed response (FolderClass missing) ```xml <t:CalendarFolder> <t:FolderId .../> <t:DisplayName>Calendar</t:DisplayName> <t:TotalCount>1</t:TotalCount> <t:ChildFolderCount>0</t:ChildFolderCount> </t:CalendarFolder> ``` ### Same folder with Default shape + explicit FolderClass (works) Request: ```xml <m:FolderShape> <t:BaseShape>Default</t:BaseShape> <t:AdditionalProperties> <t:FieldURI FieldURI="folder:FolderClass"/> </t:AdditionalProperties> </m:FolderShape> ``` Response includes: `<t:FolderClass>IPF.Appointment</t:FolderClass>` So the property exists on the store; it's just not emitted when the client requests `AllProperties`. ## Expected `AllProperties` should include `<t:FolderClass>` for every folder type (CalendarFolder, ContactsFolder, TasksFolder, Folder, etc.) since it's a first-class EWS folder property per MS-OXWSFOLD. ## Impact Outlook for Mac is one of the primary clients our evaluation team uses. Shared calendars and contacts added via "Open Another User's Folder" silently fail to appear in the sidebar because Outlook can't classify the folder without `FolderClass`. Likely affects Outlook for Windows (new Outlook / Hx) and any other client that relies on `AllProperties` to deliver FolderClass. Related to #239 (ResolveNames attributes missing) — together these two shortcomings block the core shared-mailbox workflow on macOS.