Alert on error: shared code (#207)

• Initial work on presenting alert on error

• Move Account-related error handling up the hierarchy

• Handle errors on logout

• Fix for temporary debugging

• Clean up WriteFreelyModel’s published vars

• Add error handling to top-level content view

• Set current error on API call failures

• Set current error on API call handlers

• Move User Defaults errors to ErrorConstants file

• Add default values for some error strings

• Handle purging post errors

• Add FIXME to track silent failure on fetching collections

As collections are fetched and added to the list property in the CollectionListModel’s initializer, it’s tricky to throw an error here: we call it as a property initializer in CollectionListView, which cannot throw.

Consider refactoring this logic such that we’re using, for example, a @FetchRequest in CollectionListView instead.

• Handle errors in (most) shared code

Two outliers to come back to are:

• the LocalStoreManager, where we can’t set a current error in the WriteFreelyModel in methods that can’t throw
• the CollectionListModel, where the initializer can’t throw because we use it as a property initializer in CollectionListView

• Add error handling to Mac app

• Revert "Add error handling to Mac app"

This reverts commit b1a8b8b29c7a745ea9733ed0d7266c775b534b47.