Why a google map key?

To verify that an address is in a sector with a radius, the module needs to know the precise distance from the center and for this it needs the GPS position.
Google provides a javascript API which allows the module to obtain this position with the postal address.
The use of this API is free through $200 of credit offered per month, which largely covers the needs of the module. However in order to check the usage google requests to generate a key from the Google developer console to indicate it in the configuration of the module.