[Enhancement] Add global error handler

[Merseleo]

Problem

Currently there is no consistent error handling in this frontend and in particular sometimes just any error messages are displayed, sometimes something is logged in the console, sometimes not, sometimes the error messages are shown directly to the user and sometimes nothing at all. This should be standardized and summarized in an GrpcErrorHandler.

Solution

The solution of this problem could be the implementation of a globally available error handler that can process a GRPC error object based on the status code, i.e.

• log the error to the console, provided it does not reveal any sensitive data
• map the error code to an error message if it is a standard error, such as no connection (this would display the same error message on all pages and in all cases for the same errors)
• if an error code is not known and there is therefore a custom error, forwards the supplied message
• in the default case (code unknown and no further information): “Unknown error” or similar.

This allows the error received after a request to be globally mapped to a message and displayed and the logging of errors is bundled in a central location.