I’m using the http binding to get warnings for possibly icy windshields for the next morning. Dibbler42 described a great way to do this using a jython script here but I preferred to use the http binding instead.
It worked fine for some years but somehow broke a few months ago without me noticing - it was summer, then.
During the update to OH4.3 (great job, everyone!) I saw the error message from the http thing in the logs (kudos to the new log viewer, btw!) and started to investigate:
The http thing is trying to get data from a POST request to https://api.eiswarnung.de. What is “special” about this api is that they require a Content-Type header with Content-Type=application/x-www-form-urlencoded.
But this value is unavailable in the thing configuration in MainUI and cannot be set manually in the Code tab of the thing configuration, since only the pre-configured values can be used.
My previous configuration (from OH3 days) included a “Custom header” entry, which worked fine for a few years. But apparently, in OH4(.3?) an entry from the list of Content-Types is automatically selected, resulting in the http request have two (different) Content-Type: entries.
It is possible to work around this by going into the Code tab and deleting the entry for the key contentType:. Do not delete the entire line, just the value. Otherwise it gets recreated with a default value of application/json. Save the thing and don’t ever touch it again 
It would be nice if this Content-Type header was available in the list to select from.
For reference: working definition of http thing for getting data from https://api.eiswarnung.de/:
Populating the items is done by linking all items to the same channel resultString using different JSONPATH transformations
UID: http:url:http_eiswarnung
label: Eiswarnung
thingTypeUID: http:url
configuration:
authMode: BASIC
ignoreSSLErrors: true
headers:
- Content-Type=application/x-www-form-urlencoded
baseURL: https://api.eiswarnung.de/
delay: 0
stateMethod: POST
refresh: 14400
commandMethod: GET
timeout: 3000
bufferSize: 2048
location: Draußen
channels:
- id: resultString
channelTypeUID: http:string
label: Eiswarnung komplettes JSON
description: ""
configuration:
mode: READONLY
stateContent: key=secretAPIkey&lat=50.123456&lng=9.123456
- id: last-success
channelTypeUID: http:request-date-time
label: Last Success
configuration: {}
- id: last-failure
channelTypeUID: http:request-date-time
label: Last Failure
configuration: {}