Update list of server app errors and fix assertion failure if unknown app error string is received

[michael-wb]

What, How & Why?

An unhandled app json error response from the server was causing an assertion failure when an error occurred in an atlas function was called. Unfortunately, the specific error value that was causing the failure was not captured in the customer issue.

Updated the error codes list to support the full list of errors that could be thrown by the server (from baas/common/errors.go, although the GraphQL errors were not included) and the AppUtils::check_for_errors() function was updated to properly handle error codes that were missing a string -> value mapping in the ErrorCodes class without causing the assertion to fail.

NOTE: The numeric values for these app errors was updated to fall within the 5000-6000 range, since the previous range was 4300-4399 and there are more than 100 error values. (potential breaking change)

If an unknown error string from the server is encountered, an AppError will be created with AppUnknownError and the reason string will be updated with the error string.

Fixes #6758

☑️ ToDos

• 📝 Changelog update
• 🚦 Tests (or not relevant)
• C-API, if public C++ API changed.

[michael-wb]

Superceded by the changes from the Unify Sync Error project