push MQTT settings via API

[Esc4pe]

What happened?

Was actually trying to figure out why mqtt does not reconnect when my mqtt server becomes unavailable like during a server reboot. Did not find the reason yet but this popped up when I built a workaround:

GET /api/mqtt/config returns a JSON document that cannot be POSTed back unchanged using the documented API when mqtt_root_ca_cert is populated. The form parser fails with 1002 No values found! because the data parameter becomes too large. This happens even when mqtt_tls is false.

To Reproduce Bug

curl http://IP_OF_DTU/api/mqtt/config
-H "Authorization: Basic XXXXXXX" > mqtt.json

curl -i -X POST http://IP_OF_DTU/api/mqtt/config
-H "Authorization: Basic XXXXXXX"
-H "Content-Type: application/json"
--data-binary @mqtt.json

leads to:
{"type":"warning","message":"No values found!","code":1002}%

Expected Behavior

{"type":"success","message":"Settings saved!","code":1001}%

Install Method

Pre-Compiled binary from GitHub releases

What git-hash/version of OpenDTU?

f972685

What firmware variant (PIO Environment)?

generic_esp32s3_usb

Relevant log/trace output

Anything else?

this is in the onbattery fork, but that should not have any impact I think

Please confirm the following

• I believe this issue is a bug that affects all users of OpenDTU, not something specific to my installation.
• I have already searched for relevant existing issues and discussions before opening this report.
• I have updated the title field above with a concise description.
• I have double checked that my inverter does not contain a W in the model name (like HMS-xxxW) as they are not supported.