Adds the ok_to_mqtt bit

[jp-bennett]

This adds the ok_to_mqtt bit on outgoing messages, as set by the device config. It also checks for the bit on incoming messages before uploading to an MQTT server with a known key.

Depends on meshtastic/protobufs#573

[caveman99]

Principle is ok, CI carnage needs to be addressed :-)

[GUVWAF]

Besides my comment, isn't there a better way to set this at only one place? E.g. in MeshService::sendToMesh()?
I think this would then also account for MQTT proxy.

Edit: I now see MQTT proxy is already accounted for with this, but anything that goes over the PhoneAPI is not, so e.g. if someone is doing a serial to MQTT bridge it can't honor the setting.

[caveman99]

As discussed, can we introduce a bitflag field instead?

[jp-bennett]

As discussed, can we introduce a bitflag field instead?

I love the idea, but I forgot how ridiculous Protobufs is. There is no uint8 type. The official recommendation is to use uint32 and hope it only takes only one or two bytes. sigh

Edit: Ric pointed out that I can add the int_size:8 option in mesh.options. Doing a bool costs us 2 bytes, and a single byte bitfield costs 3.