Provide access to settings through context parameter

I created the following issue on the java worker repo, but this repo seems to be a better fit. https://github.com/Azure/azure-functions-java-worker/issues/281

Currently it is hard to unit test a function that uses an app setting by reading it from the environment variables. It would be much easier if there was a getSetting(settingName) method on the context parameter, as the context parameter can be mocked in unit tests. At runtime the host can continue to read the value from an environment variable via the method in the context parameter, so there wouldn't be any breaking changes to the runtime.

Inizia individuando l’API dei parametri di contesto Java e il percorso di accesso esistente alla variabile d’ambiente descritto nell’issue. Traccia il modo in cui l’host fornisce il contesto a runtime, quindi identifica la copertura dei test unitari necessaria per verificare che un contesto simulato possa fornire un’impostazione, mentre l’accesso a runtime continua a leggere la variabile d’ambiente.

Scritto dal modello di indicizzazione a partire dal testo della issue.