AppAPI Proxy broken in some setups

[oleksandr-nc]

We received to many public issues regarding Flow app not working in some setups: nextcloud/flow#19

After a closer look, it was found that even the icon would not be displayed in this case.

I was able to dump content one of the requests in such setup coming from AppAPI to ExApp.
This is what ExApp receive from AppAPI:

GET /ex_app/img/app.svg HTTP/1.1
Host: **REPLACED**
Accept: */*
User-Agent: curl/8.5.0
Authorization: Basic **REPLACED**
Content-Length:
Content-Type:
X-Origin-IP: **REPLACED**
AA-VERSION: 4.0.5
EX-APP-ID: flow
EX-APP-VERSION: 1.1.0
AUTHORIZATION-APP-API: **REPLACED**
AA-REQUEST-ID: pSccEqBEUqy3v5Ef1bRT
Accept-Language: de_DE
Accept-Encoding: gzip

Uvicorn thinks that this is an invalid HTTP requests and rejects them.

[oleksandr-nc]

will be included in the next Nextcloud releases