Add new shelf and use database for library (see Issue #17)

[claudia3]

Description The stored shelves in the database are shown in the library depending on the shelf level. When a new shelf is created the shelf will be stored in the database and the corresponding view is updated.

Affects The whole app, therefore all team members @claudia3 @silvia-ivanova-github-rep @xSabrina @SarahKurek @LuisMossburger

Notes for Reviewer The former ListView and LibraryAdapter are replaced with a RecyclerView and a LibraryRecyclerViewAdapter. A new Fragment for creating a new shelf is added. The LibraryModel uses the information from the database instead of mock data. Integer is replaced with Long to fit the database datatype. Please review & comment/approve.

[LuisMossburger]

Forgot to say: I think before further working on this feature & merging it we should focus on finishing our Unit Tests & Automatic Testing. Let's get back to this afterwards! :)

[claudia3]

Thanks for the review.

• For the MVP i thought it is sufficient to just be able to add a new shelf to the library or another shelf so I didn't incorporate the design because you can still change it afterwards.
• Also we don't have much time left until the MVP should be done so some things like the popup to add a shelf is not usability friendly.
• The location of the back button and the name of the parent shelf you suggested sounds better than my version.
• I haven't implemented the delete feature because it is another feature in my opinion. The branch itself is called "create-shelf" so it only covers the feature that a new shelf can be added.
• In my opinion there should be no shelves with the same name in the same level because the user gets confused which shelf is the one that the user needs. E. g. in Windows you can't have a folder with the same name in the same level.

[LuisMossburger]

Agreed in team meeting:

• Design & back button will be implemented
• No two folder with same name
• Delete shelves in separate branch