Added toString methods to api.Error and api.Error.Location

[AOrobator]

The aim of this PR is to see better error messages when printing Error classes to the log.

[AOrobator]

Looks like i have a compatibility issue, but I'm not sure how to solve it. Is there a workflow for adding new APIs?

/Users/runner/work/apollo-android/apollo-android/apollo-api/build/metalava/current.txt:148: error: Added method com.apollographql.apollo.api.Error.toString() [AddedMethod]
> Task :apollo-api:metalavaCheckCompatibility FAILED
/Users/runner/work/apollo-android/apollo-android/apollo-api/build/metalava/current.txt:159: error: Added method com.apollographql.apollo.api.Error.Location.toString() [AddedMethod]
Aborting: Found compatibility problems checking the public API (/Users/runner/work/apollo-android/apollo-android/apollo-api/build/metalava/current.txt) against the API in /Users/runner/work/apollo-android/apollo-android/apollo-api/api.txt

Edit: Looks like I have to update the metalava data. i took inspiration from this commit

[martinbonnin]

Is there a workflow for adding new APIs?

Yep, we use metalava to enforce API compatibility. Looks like you found how to fix it 👍 . We should probably add this to the contributing guide or PR template.

Thanks a lot for the contribution in all cases!