(Re)adds moreByDeveloper-, similarApps- and dataSafety-field to app() and updates tests

[kluhan]

Issue solved

• #126 by adding the similarApps-field to the app-function
• #131 by updating the tests according to the new reviewId format
• #132 by adding the moreByDeveloper-field to the app-function

Problem partially solved

• #130 by adding the dataSafety-field to the app-function, which contains a summary of the data safety and does not require an additional request

[kluhan]

Issue solved

• #130 by adding the data_safety function, which returns all data safety information provided by an app.

[JoMingyu]

There are a lot of diffs, It's better to split the PRs.