wopi: onlyoffice support

collabora online (cool/code/coolwsd) seems to work thanks to #1495 however editing with onlyoffice is currently not possible

https://github.com/9001/copyparty/pull/1495#issuecomment-4959163573 mentioned they were able to open a document read-only, but I'm not even getting to that point; when I try to create a new document with the "new textfile" feature in the copyparty ui, for example with the filename `some.docx` then I see onlyoffice successfully initializes the empty document in the copyparty volume, then onlyoffice asks for the properties of the document, and then nothing more happens; onlyoffice never asks for the contents of the document, and the onlyoffice ui is stuck in a "loading" state, as if the document has not yet been transferred into the editor, however there is zero explanation why in either the copyparty or onlyoffice logs

perhaps onlyoffice doesn't like something about the wopi response sent from copyparty?

a complicating factor is that this whole feature (the wopi integration) is something i do not care for, something i will never use, so I do not have the motivation to dig into this further. I am also suspecting I have not configured onlyoffice correctly, so maybe it already works just fine?

perhaps someone with a working onlyoffice installation and a motivation to look into this could give it a shot

这个 issue 涉及与 OnlyOffice 的 WOPI 集成。首先检查 copyparty 中的 WOPI 实现，相关代码可能位于 wopi.py 或 handlers 相关的文件中。将发送给 Collabora 的响应（该响应可以正常工作）与发送给 OnlyOffice 的响应进行比较。检查 copyparty 和 OnlyOffice 的日志，查找任何错误。目标是弄清楚为什么 OnlyOffice 在请求文档属性后会卡住，并且从不请求内容。根据 OnlyOffice 文档验证 WOPI 端点和 JSON 响应。

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