Major code refactoring

Main goals are:
1. Ability to use mocks in unit tests instead of
having to setup mock web server as if it was an
integration test.
2. Cache Retrofit services in memory
3. Make it easier to read
4. Use OptIn where possible instead of propagating
Experimental* annotations everywhere

app/src/main/java/gq/kirmanak/mealient/ui/auth/AuthenticationFragment.kt

@@ -16,12 +16,10 @@ import gq.kirmanak.mealient.R
 import gq.kirmanak.mealient.data.auth.impl.AuthenticationError.*
 import gq.kirmanak.mealient.databinding.FragmentAuthenticationBinding
 import gq.kirmanak.mealient.ui.textChangesFlow
-import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.flow.filterNotNull
 import kotlinx.coroutines.flow.first
 import timber.log.Timber
 
-@ExperimentalCoroutinesApi
 @AndroidEntryPoint
 class AuthenticationFragment : Fragment(R.layout.fragment_authentication) {
     private val binding by viewBinding(FragmentAuthenticationBinding::bind)