[typescript-fetch] Support error handler in middleware

Created by: orange-buffalo

Status Quo

typescript-fetch provides support for two types of interceptors: to pre-process the request and post-process the response. However, there is one more case which is not handled - network or similar error when response is not received.

PR suggestion

This PR suggests an additional interceptor hook onError that covers the missing piece. It is called in case of exception during request processing and allows to, for instance, re-try the request, replace it with alternative route, etc.

PR checklist

• Read the contribution guidelines.
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  ./mvnw clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh

  Commit all changed files. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. For Windows users, please run the script in Git BASH.
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