Uncomfortable ExpoPushClient singleton design.

[Bryksin]

Hi

We use Spring Boot for our back-end, and based on the active profile (dev, qa, prod) we would need to either send real notification or fake it.
I saw your UnitTests and the way you mock WebServer, however, with the mock server, u manually created retrofit object with custom BASE_URL to mock WebServer and later u use raw ExpoPushService instead of ExpoPushClient

First of all your unit tests missing some coverage of actual ExpoPushClient (for example how u handle the response in case isSuccessful or failure)
Secondly, such an approach is not nicely working for dynamic beans which are based on profiles.
In real code we use ExpoPushClient not raw ExpoPushService therefore there must be an option to create ExpoPushClient object with mock WebServer and custom BASE_URL, that would allow to set up dynamic been based on the profile (mock for DEV profile and real for QA and PROD)

However, right now in ExpoPushClient the BASE_URL, retrofit and service are private static final and cannot be modified nicely.

[celandro]

There are a few other issues with the code but I don't want to get too deep into it right now.

The bigger issue seems to be this repo is no longer being maintained by the owner.