Implement API client

[ariel17]

We’ll be hitting http://www.football-data.org/ API (you can see the documentation in the site, use
the API v4) to populate the data locally and then expose it.

League code is given as input.

The data we’re importing is:
● Competition ("name", "code", "areaName")
● Team ("name", "tla", "shortName", "areaName", "address")
● Player ("name", "position", "dateOfBirth", "nationality")
● Coach(“name”, “dateOfBirth”, “nationality”) (import that data even if the values are null)