PeeringDB API calls for clients-from-peeringdb done without API key

[pierky]

PeeringDB API calls made to handle the clients-from-peeringdb command are done without the API key:

GET /api/net?asn=xxx
GET /api/netixlan?ixlan_id=xxx

[pierky]

The clients-from-peeringdb command performs multiple PDB API calls
sequentially to obtain ASNs' info. Users reported some errors related to
429s and an investigation on the PeeringDB side showed some logs where
those API calls were made without any API key.

Even though I was not able to reproduce the issue (all the API
calls were made with the proper API key) I introduce here this
workaround to reduce the n. of calls made in one minute, to match the
limit on the PeeringDB side.

[pierky]

I've just pushed out a new alpha release that contains this fix. If CI/CD will be happy, it will be available under the PyPi test instance in a few hours. It will be possible to install it by following the instructions at https://arouteserver.readthedocs.io/en/latest/INSTALLATION.html#development-and-pre-release-versions

If everything goes well, I plan to ship it as part of a new release in a few days.