[FEATURE] Delete survey responses for deleted tenant app memberships

[roberlander2]

Is your feature request related to a problem? Please describe.
When users wish to delete all of their information from the ecosystem, they must send a request to each building block to delete data as desired.

Describe the solution you'd like
Use the coreservice in https://github.com/rokwire/core-auth-library-go to make requests to the Core BB and register a callback to get information about deleted tenant account app memberships. These data should be used to determine which survey responses should be removed from the database. A RetainResponses field should be created for the Survey model, which specifies the default decision on whether to delete a SurveyResponse when a user deletes an app membership. A user may override this default behavior by specifying to the Core BB which data may be kept for each service. This data will be included in the list of deleted app memberships.

Describe alternatives you've considered
The current method of sending individual requests to building blocks to remove user data when a user decides to remove an app membership will work, but it can lead to incomplete data removal if even one request from the client app fails. This proposed change also cuts down on the number of requests the user must make manually.