Use expo-secure-store instead of Typeorm to store pings and answers data

[hesyifei]

We use expo-secure-store to store the pings and answers data as it provides simple supports for encryption whereas setting up encryption for Typeorm is very complicated.

We stores each ping data (Ping) and each answer data (Answer) as a individual keychain item. This is because keychain has a size limit (see https://docs.expo.io/versions/latest/sdk/securestore/), so it makes sense to store each element separately. We then store a list of ping IDs in a AsyncStorage item, and a list of answer IDs in a AsyncStorage item for each ping. An example looks like this:

In AsyncStorage:

• PingsList: [wellbeingStream1, interactionStream1, wellbeingStream2]
• AnswersList
  • wellbeingStream1: [anxiety, stress, sadness]
  • interactionStream1: [peerInteraction, familyInteraction]
  • wellbeingStream2: [anxiety, stress, sadness]

In SecureStore: (all encrypted)

• wellbeingStream1: { id: wellbeingStream1, notificationTime: ..., ... }
• interactionStream1: { id: interactionStream1, notificationTime: ..., ... }
• Other pings data...
• wellbeingStream1.anxiety: { pingId: wellbeingStream1, questionId: anxiety, data: ... }
• wellbeingStream1.stress: { pingId: wellbeingStream1, questionId: stress, data: ... }
• wellbeingStream1.sadness: { pingId: wellbeingStream1, questionId: sadness, data: ... }
• interactionStream1.peerInteraction: { pingId: interactionStream1, questionId: peerInteraction, data: ... }
• Other answers data...

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Changes:

• Use SecureStore to store pings and answers data.
  • Change Typeorm's PingEntity and AnswerEntity to zod's PingSchema and AnswerSchema.
• Remove Typeorm (which was added in Store data in database (TypeORM) #12).
• Migrate to @react-native-community/async-storage and @react-native-community/slider because of their better jest test support.
• Make sure all tests still work, and add more tests. (Part of Create unit tests & automated tests #11)
  • For example, in SurveyScreen.test/ tests, we now actually test the stored answers data.

Resolves #37.