Polytope-client

What's Changed
* Fix: proper file extension for covjson downloads
* Fix: handle credential config with just a user_key (bearer token)


**Full Changelog**: https://github.com/ecmwf/polytope-client/compare/0.7.3...0.7.4

* No longer uses ~/.polytope-client/keys/$USER to store credentials
* Stores credentials in ~/.polytopeapirc
* Also checks ~/.ecmwfapirc
* Fixes logging

* Add support for coverage JSON retrievals.

What's Changed
* Requests are now properly serialised, and not forced to JSON during HTTPS request creation. Python dictionaries are now serialised as YAML, which allows lossless serialization/deserialization of both JSON-like and YAML-like requests.

**Full Changelog**: https://github.com/ecmwf-projects/polytope-client/compare/0.6.3...0.7.0