Set the max_length attribute to be equal to 50 on the called_station_id
field, so that it doesn't give a 500 error(400 error instead) every time
it exceeds 50.

Fixes openwisp#467

The QA check was failing earlier because the latest commit wasn't
following the conventional commit guidelines, this commit fixes it. Ran
both the openwisp-qa-format and openwisp-qa-check commands.

Fixes openwisp#467

…uthSerializer openwisp#467

Updated the PostAuthSerializer to include a `max_length` attribute of 50 for the `called_station_id` field.
This ensures that requests exceeding the character limit return an HTTP 400 error with an appropriate error message.

Fixes openwisp#467

…station_id in PostAuthSerializer openwisp#467

Updated the PostAuthSerializer to include a `max_length` attribute of 50 for both the `called_station_id` and `calling_station_id` fields. This ensures that requests exceeding the character limit for either field return an HTTP 400 error with an appropriate error message. Added tests to validate the max_length constraint for both fields.

Fixes openwisp#467

…adiusPostAuthSerializer openwisp#467

Removed the fields `called_station_id` and `calling_station_id` from the `RadiusPostAuthSerializer`. Increased the `max_length` of both fields to `253` and applied migrations.

Fixes openwisp#467

Addressed migration check issue to causing qa-check fail

Fixes openwisp#467