Previously to view a list the user either had to add it to a tab, or tap
through "Lists" in the navigation menu to their list of lists, and then
tap the list they want.
Fix that, and show all their lists in a dedicated section in the menu,
with a new "Manage lists" entry that's functionality identical to the
old "Lists" entry (i.e., it shows their lists and allows them to create,
delete, and edit list settings).
To do that:
- Implement a proper `ListsRepository` as the single source of truth for
list implementation throughout the app. Expose the current list of lists
as a flow, with methods to perform operations on the lists.
- Collect the `ListsRepository` flow in `MainActivity` and use that to
populate the menu and update it whenever the user's lists change.
- Rewrite the activities and fragments that manipulate lists to use
`ListRepository`.
- Always show error snackbars when list operations fail. In particular,
the HTTP code and error are always shown.
- Delete the custom `Either` implementation, it's no longer used.
- Add types for modelling API responses and errors, `ApiResponse` and
`ApiError` respectively. The response includes the headers as well as
the body, so it can replace the use of `NetworkResult` and `Response`.
The actual result of the operation is expected to be carried in a
`com.github.michaelbull.result.Result` type. Implement a Retrofit call
adapter for these types.
Unit tests for these borrow heavily from
https://github.com/connyduck/networkresult-calladapter
Additional user-visible changes:
- Add an accessible "Refresh" menu item to `ListsActivity`.
- Adding a list to a tab has a dialog with a "Manage lists" option.
Previously that would close the dialog when clicked, so the user had to
re-open it on returning from list management. Now the dialog stays open.
- The soft keyboard automatically opens when creating or editing a list.
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