Feature: Clarify tags in device model documentation

[adcoly]

Description

As a user, I would like to have a clear definition of the uses and utility of each tags listed in the documentation for a device model creation through the API.
It could be interesting to have a list of those that are mandatory for a basic device model.
It could also be great to have default value of each tags (in the screen below, describing all those tags, for example).

[kbeaugrand]

@adcoly,

The documentation provides also a description of expected body:

By clicking to the LoRaDeviceModel, you can access to the field descriptions:

[kbeaugrand]

The default values information are tracked in #579